IC device?

Every once in a while, while traveling amtrak, usually on an LD train, an employee will come over the PA sysytem, and tell someone to "pick up on IC" e.g. "Jimmy pick up on IC".

What is this IC?

InterCom, for crew to talk on intercom to each other.

do they have walkie talkie type radios as well ?

Train crew (conductor, engineer) yes.

Service crew, not that I'm aware of.

I believe that is correct; The train crew have radios, while the service crew have to rely on PAs and intercoms.

When I took Amtrak in November, that's the way it went. The train crew had radios while the service crew had PA's and intercoms.