If the signal is 4G your phone could now be on the 4G800 layer which EE users with compatible handsets can use.
Until VoLTE or 4G calling is up and running BT Mobile users can't use this layer.
I have 2 phones, one with an EE sim and the other with a BT Mobile sim. In network mode with both iPhones side by side you can see often that EE has jumped to band 20 4G800 but the BT Mobile has gone to 2G.
On band 3 4G1800 or band 7 4G2600 there is no difference in signal.
If you look at BTs coverage map the 4G coverage area has dramatically increased to match that shown on the EE coverage map recently. I presume this is because BT plan to provide Band 20 800MHz 4G coverage with the VoLTE upgrade.
@steviegal the trial is still ongoing, I doubt you will see anything for a few more weeks at least. I think we will see lots of things happen as they make netowrk and account changes in preperation for the roll out.
Smart talk is totally pointless unless you are abroad. Yes, you can make calls using your home package, BUT you cannot receive them on your mobile device.