Not sure what you're asking here exactly. Certainly you can connect a 3002 up to a 3015, that's the whole point of it.
If this 3002 is currently connecting to some other companies concentrator though, you can't have it connect to your concentrator at the same time, it will only connect to one at a time and would have to be reconfigured to connect to yours, thus losing access to the other companies network.
