According to what I've read, the answer is yes, the SAE J1772 plug standard fits both the Volt as well as the LEAF and many other vehicles (though not all). One source:
http://en.wikipedia.org/wiki/SAE_J1772.
Glad to learn you've had good luck with your AV station. I've not been so lucky (repeated red trouble lights that AV has not repaired despite many calls).
Unrelated to the station plug, I thought of a few considerations to think about that may impact your use of one charger:
1. The AV charger does not have a field-replaceable cord length (so they say and advertise). I got the 15' version but a 25' was also available.
2. As you know the LEAF connector is at the front of the vehicle. The Volt's connector is on the left side between the left front wheel well and the forward edge of the driver's door. Given that, is your station installed where the cable will reach charge ports on both vehicles without creating tripping hazards, possible damage if moving one car snags the cable charging the other car, and so on.
3. Will there be any time for any reason that you need to charge both vehicles at the same time?
4. If you are on time-of-day electricity rate schedules, and if you have to charge both vehicles sequentially (not simultaneously), will the length of time to do so put you into a higher rate period for part of all of some charging?
Good luck with whatever your decision, and both the LEAF and Volt!