[The Goober]

I think its unlikely that your company will leave a tip unless it was rolled into the price that they were quoted by the bar - whichever admin set up the event and is handling the money will need reciepts for everything and can't just tack on a nice sized tip.

So either:
a) tips were included in the cost of the event, which means they will be lousy tips at best, or

b) tips weren't included and the bartenders are going to get majorly screwed

So I would just tip like I normally do. I mean, the worst that can happen is that you better service because you're the only one tipping. $1/drink is still cheap, especially when you start ordering all the top-shelf liquor you'd never shell out for otherwise.