That's been my experience. The only phone call was with CO. No big deal and nobody hassles you, although I suspect that laundering miles in this way is going to raise a flag at some point for CO when they see so many miles passing through from people who rarely fly CO. At least I've had a RT in the past year on CO...

And as reported here, the Amtrak - UA exchange is usually about a week or so. Again, no big deal and that is completely done online. Just pay attention to the annual transfer limit.