When the Rebels bring an ally, how does the Ally affect the Activation Order? Are both of these situations legal:

Situation 1:

Rebel 1 activates.

Imperial 1 activates.

Rebel ally activates.

Imperial 2 activates.

Rebel 2 activates.

Situation 2:

Rebel 1 activates.

Rebel ally activates.

Imperial 1 activates.

Situation 1 is the only legal order. In campaign you must alternate activations, so R I R I until one faction runs out of deployment groups to activate.

2 is illegal because there is an imperial group, and alternating means imperials go 2nd.

In the campaign, when it comes to "who activates next", you always alternate activating figures (or a deployment card's worth of figures) until everything has activated, starting with the Rebel player.. Rebel Allies (and Imperial Villains for that matter) are not an exception to the alternating activation as they are treated as "friendly groups" under the direct control of the Rebel (or Imperial) player.

Reference:

Allies, RRG, Page 4:

Allies follow all rules for other figures that have Deployment cards. The ally is considered to be friendly to any other figures controlled by that player and other friendly players.

Activation, RRG, Page 3:

After resolving an activation, exhaust the figure’s activation token (for heroes) or Deployment card (for all other figures).

If all friendly groups are exhausted, that player cannot perform any more activations this round. The player’s opponent(s) continue to resolve activations until all groups are exhausted.

Note: In skirmish battles activations can be delayed, but I wont go into that here.

Thanks for the responses guys!