Yes - I use the insurance disc from my daily as that's the policy that you will be driving under too.
Just check with your existing insurer - I was with 123.ie (RSA) previously and they insisted that the other car you're driving had to have a valid insurance policy in place by the owner (no idea why) but FBD said it didn't have to be insured in the other 'owners' name as it was them covering the liability.