They do not have to receive GPS, but it causes issues for e911 service if they do not. It has no impact on anything else, at least not the T-Mobile version.
The one I had, an AT&T Microcell, which was the only model offered by my cell provider, refused to work without a GPS signal.
The one I had, an AT&T Microcell, which was the only model offered by my cell provider, refused to work without a GPS signal.