I'd like to know, from others experience, what solutions might be best for configuring OpenSER routing from a PSTN gateway to multiple IP PBXs.

I guess there may be various solutions ranging from quick and dirty to the other extreme but Id be interested to get some ideas what are typical solutions for others. As OpenSER is so configurable and there are so many optional modules its quite hard, coming from zero exposure to any production SIP envrionments, to know how best to go about this...