It depends on what requirements Beta software engineers are needing. It can be a bit tricky with network provider software that's been added to a phone. Generally it's the network provider that pushes updates out to the phones.
My old Huawei P30 Pro I got from O2 and I was able to join a Huawei Beta program and that had O2 specific software.
But with the One UI 5 Beta, the requirements are for unlocked devices only.