I don't think so. I've found one blog that says they take over abandoned holes, not ones that are currently in use.

http://bugeric.blogspot.com/2012/10/wasp...

Carpenter bees do sting - at least the females will, if severely annoyed or handled. Males can't.

Thanks! I didn't realize the females stung, but I did read that they tend to stay in the holes while the males guard the air outside.

I don't really like carpenter bees digging in my deck, but I do think they're cute and I like that they don't sting and that they chase away bees that do. Lately though, mason wasps have started showing up, and I've seen them go in the carpenter bees' holes, and the carpenter bees have been quickly disappearing. Are the mason wasps killing them?