I am not sure about obi features, but I know for a fact having programmed hundreds of alarms most technicians just enter a random time they don't think you'd be awake to use the phone for the weekly or daily test, you could ask them to change it to an earlier time like so if it does ring PH1 it's not a nuisance. That's the cost of a service call though =| and booking time to have them show up.
Hopefully someone else knows a way to do this from the obi I know you can filter caller ids, and phone numbers, but maybe you can try something like this I use a blacklist custom user digitmap enter into my X_InboundCallRoute and it sends the calls to no where and nothing rings, and my VoIP provider just asks them to leave a voicemail. I am not sure if it only filters callerid/phone numbers but you could try this modifying this.
{(MBan):},{ph1}
maybe try putting this line below in your inbound call map for PH1 that should send the call to nowhere? I am only guessing here, I am no Obi Expert myself but it could work. I'd recommend Saving/Exporting your current configuration so you can revert back to it easily; Then add the code below to the beginning of your
X_InboundCallRoute {(ph2):},{ph1}
I know you can filter inbound calls on ph1 and forward select callers to ph2, I do that for people calling looking for my housemate on my number, so I don't have to be bothered by them. My phone doesn't ring, and theirs does.