I'd never thought of them for vacuum lines, but I've used similar push-to-connect fittings often enough for plumbing pneumatic controls. The stuff I've used was Norgren, but it's very similar. If they work just as well for vacuum, you're right, that could be very handy.

Depending on just what one needs (configuration and tubing size,) they might be conveniently available from MSC. I know that they stock some of the Norgren and Legris fittings (unions, tees, Y connectors, crosses, elbows, pipe thread adapters, etc.) I've always found MSC to be easy to deal with, and good golly, they stock a lot of stuff!