Back in the days of CAP648 I worked for two companies who accepted each other's paperwork and ground training but we still did separate base checks for each company. Throughout 20-odd subsequent years of freelancing, just about all of which was AOC whether under 648, JAR or EASA, I've always done the intro and OPCs for each company I worked for; in some cases the separate OPCs for two companies were conducted by the same examiner, who was nominated in both operators' Ops Manual Part Ds. Same applied for line training at a new operator - even though I was a Line Training Captain at other companies (admittedly, this was somewhat truncated). Companies have accepted ground training from other operators where the training provider was the same but as time has gone on this has happened less and less.
As has been noted above, the OPC is an operator-specific check and it's difficult to see how two AOCs might share an OPC unless their Ops Manuals, paperwork, procedures, limitations and training requirements are identical.
Last edited by Sepp; 11th Jan 2017 at 19:22.
Reason: Must remember to check for spelling errors!