reply to buddahbless
Re: Seems you would want to deploy in densely populated areas Until they are all LTE, it's a no go as their voice networks aren't compatible. GSM based phones run the data and voice over the same radio, so unless they put in an extra radio for roaming, which doesn't make much sense, t-mobile can't roam on Verizon.
Even after Verizon and T-mobile have VoLTE, roaming would only be a possibility if their VoLTE systems are compatible. In other words, it's a real long shot