For the transmission of an MBMS content to a plurality of user equipment units, the use of a p2m channel may only be beneficial if the number of joined user equipment units exceeds a threshold. However, counting is made difficult due to the fact that idle mode UE, also a non joined UE, may reply to the notification, and hence pretend a higher number of UEs which are ready and able to receive the MBMS content. According to the present invention, when joining the MBMS service, a number which is only known to the user equipment unit, as well as to those RNCs which will deliver the MBMS service for which the UE has joined, is provided to the UE. Whenever the UE replies to a service notification, it uses this number. The RNC determines a corresponding number and in case the number received from the UE matches the number determined by the RNC, the UE is counted. Advantageously, an integrity protection may be provided for the notification reply for joined UEs which are still in the idle mode.