EAP-SIM Broker?

Hi Guys, does someone know a way to do real EAP-SIM authentication with (through!) freeradius? Most if not all GSM-Carriers have radius-servers for their own WiFi-Hotspots, but obviously they wont give anyone access to them but only Hotspot-Roaming-Providers like iPass or WeRoam. Is there some sort of broker-service that would allow this? I would imagine a concept where i pre-filter the authentication requests and only pass the imsi's i want to be able to access our wireless network to the broker for real authentication... This is for my employer, so no problem if there's a fee for this service involved... Regards, Andreas