A Resistência sabe que o R2-D2 tem o resto do mapa?

• NÃO.

  Eles nem sequer sabem que o mapa que Poe deveria recuperar não era o mapa inteiro em primeiro lugar . Isto é o que acontece na novelização de Alan Dean Foster quando eles primeiro veem o mapa:

  Reaching in, C-3PO removed a tiny device. Turning, he inserted it into a matching slot in the multi-sided table-projector that dominated the center of the room. Immediately, a three-dimensional map filled the space above the flat-topped apparatus with stars, nebulae, and other stellar phenomena. Leia studied the display intently. But though her eyes roved knowledgably through the compacted cosmos, she failed to find what she was looking for. Her dissatisfaction was unmistakable.

  While he was in his own way equally disappointed, C-3PO was not programmed to display it. Instead, he merely expressed a rational regret.

  “General, while I have already completed a preliminary analysis, I’ll inform you of my final determination only when I have finished comparing the information available in this map to that in our full database. There. I’ve finished. Unfortunately, I have to conclude that this map contains insufficient data with which to make a match to any system in our records.”

  From a corner, Han spoke up. “Told you.”
  Leia ignored him. “What a fool I was to think we could just find Luke and bring him back.”

• Isso também é confirmado por eventos anteriores: Poe discute todo o mapa (não um fragmento ausente) com Tekka:

  “Legend says this map is unobtainable,” Poe noted. “How’d you do it?”

  e quando conversar com Finn:

  “My droid’s got a map that leads to Luke Skywalker.”

• Obviamente, o fato de o mapa estar incompleto é novidade para Finn, Rey e Han e BB-8, porque eles simplesmente concordam com o que Poe disse ao Finn:

  Dutifully, the droid rolled into a suitable position. A lens brightened, and abruptly the lounge was all but filled with an enormously detailed and complex star map. Nebulae, solo stars, translucent splashes of concentrated dark matter, and entire solar systems were displayed before them. Even Chewbacca sat up to have a better look. Finn was impressed and Rey in awe — but Han found himself frowning.
  Moving forward and into the three-dimensional representation, he tracked system positions and locator stars. One finger traced the outlines of a particularly bright and well-known nebular cluster. Like everything else in the map, it was brilliantly depicted.
  It was also only half there.
  He turned to the others. “This is accurate, but it’s not complete. It’s just a piece. I can tell from the location of the breaks and from what’s only partially shown.” He grunted softly. “Ever since Luke disappeared, people have been looking for him.”

• E como um prego final, descobrimos no final que Poe foi informado por Kylo Ren que é apenas um mapa parcial

  Never one to defer in the presence of superiors, Poe spoke first.
  “Kylo Ren said that the segment held by Beebee-Ate is the last piece of the map that shows the way to Skywalker’s location. So, where’s the rest of it?” “The First Order has it.” Rey looked over at him. “They extracted it from the Imperial archives.”
  Poe stared at her. “The Empire?”
  Admiral Statura nodded in agreement. “It makes sense. The Empire would have been looking for the first Jedi temples. In destroying all the Jedi sanctuaries they would have acquired a great deal of peripheral information.”

  Note que Statura basicamente admite que eles não tinham ideia e ele está concordando com Poe por pura lógica, não por conhecimento prévio.

• Dito isto, o BB-8, por alguma razão insondável, parece que R2-D2 tem o resto do mapa, embora não seja explicado em canon por que (para ficar claro, ele só sabe sobre o "resto". do mapa "porque Rey e companhia o viram mais cedo, enquanto no caminho).

  Isso acontece logo depois que Poe e Finn se reúnem:

  THE SEARCH HAD taken BB-8 some time, but he finally found what he was looking for. Or rather, who. Or maybe both, since an intelligent droid technically qualified as both a who and a what. In the dark, dusty storeroom he rolled over to the R2 unit and beeped a greeting, the transmission sequence too rapid and too exhaustive for any human to follow. It didn’t matter. There was no response from the immobile R2 unit.
  BB-8 tried again, utilizing a different droid language. When that also failed, he moved forward and gave the other mechanical a forceful nudge. Like everything else, that too failed to generate a response.
  Observing the unsuccessful interaction, C-3PO came forward out of the shadows.
  “You’re wasting your time, I’m afraid. It is very doubtful that Artoo would have the rest of the map in his backup data.” When BB-8 queried the protocol droid, C-3PO responded without hesitation.

  Só para ficar claro, a ideia não era da C-3PO, ele simplesmente descobriu o que o BB-8 estava dizendo.

Eu acho que é bem claro que não; Leia, por sua vez, parece extremamente desapontada que o mapa seja apenas uma peça. Em nenhum momento alguém "espera, parece que se encaixa no mapa do R2-D2!" Eles também não parecem ter nenhuma ideia do motivo pelo qual o R2-D2 foi desligado ou o que o acordará.

Eu também ouvi a idéia de que o BB-8 sabia e ninguém o ouviu, mas também sou cético. Muitas pessoas na Resistência falam a linguagem do BB-8, e eu tenho certeza que se ele dissesse "Eu sei onde fica o resto do mapa", alguém teria prestado atenção.

Eu acho que devemos interpretar parte do flashback de Rey na cantina, que mostra

Luke putting his hand on R2

como o mapa sendo carregado no droid, junto com o comando para desligar até

Rey (or at least another Force user)

volta para reivindicá-lo.

O BB-8 pareceu pensar que o RD-D2 tem o resto do mapa, mas o C-3PO descartou essa ideia e depois mencionou que se fosse verdade, seria inútil porque o R2-D2 estava em modo de baixa potência.

Assim, a resistência poderia esperar que R2-D2 tenha o mapa, mas eles não puderam ativá-lo. Então eu acho que eles não sabiam.