I'm an ICE student, and yes I have a university card and life membership to the cambridge union. The university card isn't optional, you're automatically given one upon enrollment.
As for the almuni camcard and cantab.net I'm unsure, since it may require marticulation. Not all courses in ICE require marticulation, (only the postgraduate programmes I believe). But we do have university emails like any other student.
At the moment, I have full access to all facilities and societies/events within the university, all you need is a university card.
Edit: If you do want to join the union I recomend getting life membership during the freshers period. They offer a small discount during this period.