some team abilities specifically state that 2 adjacent characters, in order for the TA to work, have to both have the same TA:
injustice league: "when 2 or more friendly "injustice league" team members are adjacent..."
defenders: "a member of this team may use the unmodified defense value of any other adjacent friendly "defenders" team member..."

but some do not specifically say the adjacent fig has to have the same TA:
x-men: "...in which 2 friendly members of this team are adjacent..."

in order for TA's that require 2 or more to be adjacent to work, do they all have to have the same TA?

When a team ability requires more than one team member to work, it is manditory that the other figures have the same team ability (or are copying that team ability).

sounds pretty straightforward!
thanks

There is the Morlocks team ability... It only requires friendly figures be adjacent to the Morlock. They don't have to have the same team ability.

You have to look for the phrase "this team" or "this ability" in the team ability. Typically that means they have to have the same team to work.

A little extra clarification:

a "team" is a group of figs sharing the same Team Ability.

A "force" is the group of figs that you are using in a game. "Army" is another way of saying it.

So, when a TA refers to "team", it is refering to other figs with the same TA.

Hope this helps...