I get 128kbps - 512kbps on "Extended Network LTE" and I'm 99% sure it's on AT&T's network.
I get about 5mbps/5mbps on "Extended LTE" and I'm not sure if it's Verizon or T-Mobile's network...
Neither of which seem to go towards my 300mb data roaming limit. The only thing that seems to go towards that limit is "Extended 3G" which is on Verizon.