hello,
I don't know if I understand your request.
You can bridge ethernet frames over a T1 WAN link but in order to deliver them at a remote end ethernet LAN port on another router.
How can an ethernet frame be compared with an HDLC or PPP frame ? They are different.
It is easier and possible to route between the T1 link and the ethernet where is the ASA. Of course you will need to modify ASA configuration but it shouldn't be so difficult you will need to change the default-route ip next hop.
Hope to help
Giuseppe