Since this seems to have been around before the OVA, we don't know for sure what kind of dirty tactics they were talking about.
If it's about the cardboard mockups, I don't see them as a particularly dirty trick, merely a more elaborate one.
Besides, if we were to talk about dirty, how about Yukari's knack of snooping around in a false uniform?
Hnn~ they don't have much funding...But if it's you guys then I'm sure you'll do fine.How's your confidence level?That's the case, apparently....but I heard they fight using some pretty dirty techniques.