Is the other gateway also a cisco gateway. You should be able to do a transfer, the only limitation is that all gateways or devices should support h450 for the transfer. I assume you are running 12.2.15ZJ which has h450 capabilities, your other gateway with the e1 should also have the support, otherwise you can download the h450 transfer tcl script from cisco.com.
Please look at the link for more details.
http://www.cisco.com/en/US/products/sw/iosswrel/ps5012/products_feature_guide_chapter09186a00801812db.html
Taimoor
