They could but they would have a lot of developers sniffing around the edges trying to figure out if HP was really serious this time. Last time I went to their developer conference they said they were really serious, and then 3 months later dumped the entire thing.
Unlike Google, they actually had a decent tablet OS. They had ceded the smartphone market to Apple and Google. But at the time the only real tablets were coming from Apple. Some idiot bean count of a CEO saw the competition (iOS and Honeycomb) and got scared.
Enyo is still under active development, so no, they didn't snag the entire team despite what was inaccurately reported in all of the tech blogs at the time.
They don't have any hardware to run it on. The Touchpads are shutdown, finished, gone. The tools have been dismantled and the workers sent elsewhere. Enyo is little more than a project looking for a purpose at this point.
I am surprised people don't talk more about how badly HP messed up WebOS.
If they had put their weight behind it and licensed it could easily have given Android a run for its money and at the very least knocked RIM squarely out of the market.