new UM card with +1/+44 dual number soon

[inquisitor]

I've no idea, whether UM 44/1 SIMs may roam on further networks, but US coverage and those US numbers are realized by a cooperation with an American MVNO.
Basicly the UM 44/1 SIM is two SIM cards in one: a regular UM+ SIM with Jersey identity and an American one from that MVNO. Subscribers will be able to switch between those two SIM identities by SIM toolkit (that's the menu, where you can request callbacks and check your credit with current UM+ SIMs).
So maybe you guys can identify that MVNO, who offers service in Pennsylvania and has roaming agreements with T-Mobile and AT&T. The US roaming capabilities of 44/1 should be the very same like of that MVNO.