The way I've interrpreted it, in order to share in the benefits of a TA, you either have to have the TA yourself or currently be wildcarding it.
Veteran Thor stands next to a friendly Rookie SHIELD Agent. Agent can't use his TA to boost Thor's damage, correct?
Same with Defenders, Anti-Spiderman gang, Gotham P.D., etc., right?

Are there any you can do this with?

Thor does not have to be a member of SHIELD to have them boost his damage dealt. SHIELD can be used to boost the damage dealt by any adjacent friendly character performing a ranged combat attack, not just other SHIELD members.

Some team abilities do require the characters sharing in the benefit to be of the same team (or a wildcard) such as Defenders or the anti-Spider-man (Sinister Syndicate) team. In these cases it is explicitly stated in the rules for these team abilities that the values can only be shared with members of the same team. X-Men is another example where it only works between two X-Men.

Hydra is the classic one you can plus up with any friendly figure (cause it doesn't take an action and wc's nicely to vangards of Doombots).

Paz

I think SHIELD agents are going to start seeing a lot more use in our games...

Just because I'm bored:

These TAs require 2 or members to use the TA:

Batman Enemy/Sinister Syndicate
Injustice League/Masters of Evil
JSA/Defenders
Superman Enemy
Titans/X-men
Fantastic Four

And these only need one fig to use the TA:

Avengers/Brotherhood/JLA/Top Cow
2000AD
CrossGen/Mystics
Crusade
Danger Girl/Skrulls
Kabuki/Batman Allies
Green Lantern Corps
Police/Hydra
Superman Allies
SHIELD
Power Cosmic
Kingdom Come
Suicide Squad

And, of course, the Wild Cards:
Minions of Doom
Spiderman Allies
Legion of Superheroes
BPRD