I think it depends on what kind of net this is. I am facing similar questions working in the VoATM telephony industry.
In such a case, where only PVC’s are used, traffic models take into account the following factors:
BHCA, Call setups per sec, Parallel calls, BW needed per call
But I know of no model for a network with both PVC’s and SVC’s.
The answer to your question might be useful to me too!