I actually posted this same question a little while back on this same theread, #25, but no one responded so I assumed no one knew.
I can tell you this. When the factory alarm is armed, and I use the viper remore to unlock, it does not disarm the factory alarm. However, when the factory alarm is armed, and I remote start the vehicle, the factory alarm automatically disables.
I think the remote starter disables it by the bypass that is supposed to be installed, but is not installed on mine. I have about 10 relays that do the job.
Just by starting the vehicle without pissing of the passlock or whatever it is, the factory alarm disarms itself.
I think the H3 such as many other cars should have at least a factory alarm disarm, however it may not have an arm input.