I think this would work by taking the lines that come out of the obi and splitting them to your various phones. So when the obi rings line 1, all your phones ring on line 1. One picks up presses hold and another phone picks up line 1.
I have two obi 202's on the way to me as I am trying to do this exact same setup. We want our 6 4-line phones to work with two obi 202's (4 lines total).
In fact, the support guys told me we could setup a mock hunting group, so if line 1 is busy, line 2 will ring...line 1,2 busy, line 3 rings, and so on.
Here is what he said:
"If you plan to use analog phones with our service you can get the 2 OBis and register the 4 lines by creating sub-accounts. You can disable the call waiting feature in your obi device and add a Failover to the DID number (for Busy instance), this way when a call comes in, you can route this call to either a sub-account (or line) or maybe an external number (your cellphone), for example."
Hope that helps you out. This would make a pretty nice setup.