Proxying based on AVPair (multiple SSIDs)

[Jason Carr]

I'm running multiple access points with multiple SSIDs on each access
point.  We have some groups that want to run their own RADIUS
authentication, and we need to proxy their requests.  Cisco access
points have radius servers configured only by device not by SSID, so I
need another way to figure out which SSID the client connected with.
Our certificates don't include an @ sign in the username, nor do I know
what authentication method the other groups will use.  

The only other method I can think of to proxy off of other than realms
would be a Cisco AVPair, which is already being sent to the radius
server.  There is one called SSID, which contains exactly the
information I'd like the proxy to forward based on.

Anybody know if this is possible with freeradius or another software?
If so, any configuration file contents I would need to set this up.

Thanks,

Jason