Ok, CS PAGING is going through the PACCH, so it will not impact Abis or Ater interface. Regarding Gb interface, it should not be a problem either, because the amount of users that are in PTM and are also receiving a CS call is very low. IT can happen, but that is going to be a very small amount of people. And only their own PAGING will go through the Gb… so it will definitely be very small.
I wouldn’t worry about this.
You could have a look to 3GPP 23.060, it gives a good overview of what “new” signaling will be generated by the establishment of a Gs interface.