Edit - Short version: No, you can't use K'mtar, but you can use some other ones.
Here's the order things happen in when you play a card (per the rulebook, page 18):
1) Ability to play the card text.
2) Cost text
3) Costs are paid
4) Mandatory "prevent" text
5) Optional "prevent" text
6) Mandatory "when you play" text
7) Optional "when you play".
At each step, the active player chooses the order of things that go at each step.
Friction is at step 6. Here are examples of each step:
1) Playing Kira Nerys,
Starfleet Emissary to Bajor. Friction won't stop her from being playable to Bajor (or Cardassia).
2)
Matt Decker: Friction doesn't stop him before he can be used to destroy Friction.
3) This step just means that you subtract the cost of the card from your available counters this turn. Friction won't prevent that from happening.
4) This one doesn't come up very much. I can't think of an example that relates to Friction, but
Sabotage Program is mandatory prevention, and would trigger before something like
Grav-Plating Trap in the case of an event being played.
5) This is where
Cascade Virus hits. Any ability that triggers after this point (for example, any "when you play" ability, mandatory or optional, except cost-related ones) would get stopped by Cascade Virus.
6) This is where Friction hits. But, as the active player, you get to choose the order of events. So, if, for example, you play
Annexation Drone, you, as the active player, would probably choose to score the points first, then he is stopped.
7) This is after Friction hits; these abilities (such as the one on
Alexander Rozhenko, K'mtar) will not happen if Friction is in play, since they are optional (have "may" in text).