Oscam's biss handling was re-written more than a year, and some thought was put in to network sharing. I helped write it, so you can trust this advice:
1. The biss CAS has no ecm, but oscam creates a *fake* ecm on channel change. That fake ecm only weakly identified the feed, meaning network shares would likely return bad Cws from poorly matched feed <-> SoftCam.Key lookup.
2. This fake ecm was enhanced so as to better identify the feed: the enigma2 namespace was added so as to include orbital position, onid & tsid, alongside sid & A/V pids.
Thus, if your clients are *enigma2* boxes (or properly inject namespace etc into the CA_PMT), then all is fine having one central server / keyfile, with oscam-emu on the clients. But you *must* use the namespace hashes in your SoftCam.Key, as the legacy/weaker fake ecm matches are ignored for all network ecms.