That's certainly a possiblity. Although I don't think this is like beta, it could be, but if players are required to advance through pbs at a 'live' rate, they will need to be on the test server for a significant amount of time.
And if it's uncontrolled, as in active PVP happening while players are trying to test pbs building functionality, it will take even more time. This holds true if we're also going to have to mine to build on the test server.
If the devs, or players, are thinking Test=Beta, then players will have to make a choice between playing on the live server or testing on the beta server; my guess is beta would win.
If its a 'test' server though, and clients log in with prefit bots, modules and extensions and a general plan of "defend the pbs" or "Attack the pbs", that could provide valuable feedback.
And at other times, you log in and get a symbiot with Terraforming modules to test with.
Ideally, it would be a pre-developed plan.
Week 1- players test terraforming
Week 2- players test/build PBS
Week 3- players attack/defend PBS built in week 2
And, of course, all along material, NIC, and bots are simply preloaded into the agents so time can be spent on testing and not gathering.
Edit: Or as you said, have it all on the market free.