It sounds like the second bullet fits the scenario you are describing. Reading that bullet, it sounds like you'd have to get the master/administrator User ID/Pass which I'm not sure any IT Dept would be willing to give up. Perhaps they'd help you authorize it though, not sure how things work at your company.
Maybe post something like this on AT&T Support Forum? Not sure if there could potentially be any additional charges or not
Another thought, I'm guessing you want to be able to sync your work appointments/meetings on your watch, which is why you are looking to pair it with that phone, yes? Is it possible to sync your work calendar to another calendar app to get the notifications that way?
I had a perfect setup which was my personal mobile phone, stipend and I was able to get work and personal mail on my phone. Then the company decided to implement an MDM and at that point I decided to take a work issued phone instead. I don't like having to carry two phones with me at times but to be honest, I appreciate the separation of work and personal life.
