Pain, we're not sure on this -- I haven't seen a public answer from Valve one way or the other yet.
From a technical standpoint, it shouldn't be too hard for us to add it to our existing rental infrastructure. The extra work comes from having to support a beta product that lacks features, has a significant amount of bugs, and is constantly changing. CS:GO is still deeply in the beta phase right now (servers don't even support >10 players yet!).
I'd like to see beta servers up for managed machines to test things out.