The only civil units that can provide a radar service without Primary radar are those within Controlled Airspace, and they can only provide that service within CAS. Once the primary goes outside CAS then you're going non-radar and you shouldn't get a radar service.
So - in answer to your question - YES, they can see primary contacts
The military seem quite happy to provide a radar service without (mad!) but you will be told that traffic info will be given on transponding aircraft only.