Hi Steffen,
to my knowledge it is possible to retrieve RTCP data from a AudioCodes gateway. Just because the Prognosis collector for AudioCodes gateways does not collect them yet you might have to integrate the gateway as a AudioCodes SBC in Prognosis. Reagrding Syslog Prognosis can of course retrieve it but there is no default packaging for special syslog alerts yet, you would have to review it and build them.