Loyalty

After forces are placed in their starting areas but before the first player's first turn, each wild card must choose a team ability that can be copied by wild cards and is possessed by a friendly character. The wild card possesses the chose team ability until the end of the game and can't use any other team ability.

So according to this your wild cards would not just use, but possess the team ability. Would this then allow your wild cards to share their values with other Defenders or Sinister Syndicate? Could R Taskmaster then share his 11 attack with the Sinister Syndicate again?

That is correct.

Correct. However, some game effects still rely on team symbols... so the wildcards would still have their normal team symbol (MoD, LoSH, Spider-Man Ally, etc) and not the symbol of the TA they now possess.

And would they still hold on to the TA even after all the printed TA's were removed from the board?

From the Player's Guide:

LOYALTY
 Wild card characters retain their chosen team ability even if the character with that team ability is KOd.
 Wild card characters would choose their team ability regardless to any feats (like Siphon Power, Saboteur, alternate team abilities) assigned to either team before the game begins. They would retain that team ability for the game.