Dual NAM used to be very popular back in the AMPS days; these days people simply buy multiple phones. US carriers will still set up Dual NAMs (it's totally unrelated to cloning) if you are knowledgeable and manage to get someone who's more than averagely competent (and your handset supports it, of course, which is precisely what the OP is trying to determine with the TP2).
tjienan, I'll poke at that registry key in a little while and report back with my findings. My TP2 is with Sprint, who historically doesn't support Dual NAM (they never had their own AMPS network, and therefore customers expecting the ability, even 20 years later...). So, a negative won't rule out the ability, but a positive would bode very well for you.
For those of you unfamiliar with Dual NAMs and are equating it with cloning, it's no more cloning than your office phone with 2 outside lines. The hardware supports it, the network supports it, and the operator supports it. It's totally legit, but isn't something usually requested by the Average Joe, as it's almost always been a "business" feature.
UPDATE: I've tested. The registry key quoted on page 2 does indeed give the Switch NAM page. \Windows\switchnam.htm has full instructions on what to do once you've set the registry key. It doesn't even look like you need to do a soft reset! I couldn't actually test, as I only have 1 NAM, but it appears the handset certainly supports it.