Raven guard infiltration

How many troops can they infiltrate? In matched play you're restricted to one of the same each turn, does that mean only one squad can infiltrate?

Matched Play section of rules covers this. The Mac of one command point per phase does not affect CP used before or after game. Or other abilities not during a phase.

I would not worry too much about it. Since it is infiltrate and not DS, there is a good chance they will lose their infiltrators if they get too close and lose initiative. Its a very risky move to do if made aggresively.

You don't have to be too aggressive with it in order for it to be valuable. I can think of several good uses for this. The most obvious would be centurions or devs on top of that LOS blocking ruin in the middle of the board, or a squad of jump marines with flamers, out of LOS on the flank to distract you from the three scout squads that has infiltrated in to cover on the other side.
All depending on the board of course.

Yea. But still risky. Thats all. Its useful, but not especially powerful tactic that can backfire.