For the core book, it seems like your answer here
implies that a character can "maintain" a Concentration(Lasting) or Sustained (Lasting) power with the appropriate action and/or concentration check despite having switched said power out for a different Alternate Power in an Array. Do I have this correct?
Side note for clarity: I put quote marks around "maintain" because Sustained Lasting powers in core (and UP) do not stop working entirely just because you aren't "maintaining" them. Concentration(Lasting) Duration powers in core stop working entirely if you don't maintain them, though this is different in Ultimate Power. I presume I have all of this correct.
In Ultimate Power, is the answer the same as in 1a)