We currently do not have PSTN set up for these Collaboration labs. you can call to other endpoints registered to your sandbox though. Is this a feature you would like to see introduced?
It would be a nice feature to have. Although the lab is sufficient for testing. Calling outbound numbers only proves gateway configurations which can be tested with other methods. I use a lab that I built for that sort of stuff, with multiple gateways and routers. It never hurts to have a few of those around to build and test with.
Thanks Joe, I will test it with a physical UCM then.