Hi
It's many years since I was in the semi finished plastics industry but from memory ABS machines well though with a high speed router you need to keep the feed quick enough to stop chips sticking and welding after the cut. I used to set my Elu to it's lowest speed.
Standard HSS or carbide cutters worked well for me and spiral single flute especially. It's commonly fabricated materiel so do a search and I'm sure you'll find loads of info on the internet.
cheers
Bob