Quick and dirty:

Mirror Master is in a 100 point game carrying Mockingbird. MM uses his TA to copy Avengers TA. He does the transporter move and attack while depositing Mockingbird next to an opposing fig.

My question is: can Mockingbird attack? Is the transporter move and attack a 'free' one like it is when someone like Aurora or Northstar attacks with HSS.

Thanks in advance. I should probably know this but it's been forever since I used Hawkeye or Black Knight (transporters that have Free Move) so I can't remember.

A few details. Since MM is copying Avengers and transporter ability lets you use a move action and attack, his action does not take away an action from your allotted actions, but it still is a tokenable action and is not a "free action."
Since his Transporter attack must take place during his movement, he must have sufficient movement to move at least one more space after becoming adjacent and attacking.
Mockingbird CANNOT attack. The rule is NAAT (No Action After Taxi.) No matter how you were carried, you cannot take any action other than a Free Action after you have been replaced on the board.
HSS attacks can no longer be used without taking an action. HSS option 1 used use a Move action, now it is a Power action.

edit: WOOHOO! I beat Normalview!

She's been carried, so no.

HSS is now a power action; Avengers/JLA/Brotherhood/etc TAs only with move actions. So if Aurora uses HSS, it will count as one of your actions for the turn.

As Transporter move and attack is a move action, that can still be used with Avengers and such.

No idea why I thought the Transporter carrying someone would be any different than a flyer. Brain lapse there.

As for the second part, thanks. Man, they really nerfed HSS this past rules session, didn't they.

Slightly offtopic, but I realized there is a little stunt you can do with E Mirror Master: If you slap Flashbang on him, he can use it in conjunction with his Transporter move/attack. Of course, he can only move 4 spaces while doing it...