I believe that Tony thinks he is straight, and maybe tries to convince himself that he is straight. I don't think he's exclusively gay, but he definitely has some same-sex attraction going on and is at the very least bisexual. I think he appreciates beautiful women, but possibly more in an aesthetic manner rather than a sexual manner. He might try to convince himself that he wants to have sex with them, but the fact that we haven't seen him go on a second date with anyone but Jeanne -- and she was an assignment -- leads me to wonder why.

With Tim, he's probably been fighting his attraction since Day 1. He probably tells himself that it's inappropriate due to the fact that they work together, or he tells himself that he couldn't possibly be attracted to Probie/McGeek/whatever he calls him, or he tells himself that duh, Timmy is a GUY, and Tony doesn't do guys (yeah right.)