From what I have seen, you don't have to be "in the TF giver's zone" to invite them, but you DO have to be "in the proper Alignment's side".
Not sure if it is something in the way the Hero/Villain alignments are treated when dealing with Rogues/Vigilantes, but from my limited experience, it seems to work as follows:
- Assume the person starting the TF is a Hero, and they are starting Positron's TF (Steel Canyon).
- If you are a hero, they will always be able to invite you, because you will always be in a "hero" zone.
- If you are a villain, they will never be able to invite you, because you will never be in a "hero" zone.
- If you are a Vigilante/Rogue, the game will treat you slightly differently:
- As a vigilante, you are always considered a "Blue" to "Blue invites".
- As a Rogue, you are only considered "Blue" to "Blue invites" if you are in a Blue zone (ie, you shouldn't have to be in Steel Canyon for the invite to go through, it should work even if you are in Atlas, or Talos, or Founders Falls.
- Haven't tested neutral zones (such as Ouro, Cimmeroa, or Pocket D) enough to know how they work as far as group invites go, but I imagine they probably follow the same rules as above.
Basically, it seems to be the alignment of the zone you are in that is what actually determines their ability to invite you (when it comes to Rogues/Vigilantes) rather than the Alignment flag itself. Which leads me to believe that the game still considers Rogues to be Villains and Vigs to be Heroes (also supported by the fact that you can only access H/V Base Alignment missions from Ouro Crystals instead of both sides), and only really flips the switch when you are actually visiting the other side's zones.