Technically, yeah, but the server ops of both networks have to agree and make sure their configs and services are the same and then join their networks together by a link. But you're never gonna get EFNet to link to something like Undernet or DALnet. They all have philosophical differences.

yeah we used to run bridges that used two bots and DCC to relay the messages. It worked sometimes but in my experience this is more trouble than it's worth aside from simply demonstration.