[otrs] Remove Ticket# field when replying to certain tickets

Hi , Is it possible to remove the "Re:Ticket#" when replying from only certain tickets , the reason is , we have another company who uses a call logging system as well , which in turn adds its own Call nr , now it seems OTRS is interfering with the subject line (which needs to be kept intact for some reason). I know it is impossible to not assign a ticket to an incoming email , I also looked at Filtering rules , but there is no indication of this being possible. Has anyone come across such an unique problem/solution? Any help suggestions will be greatly appreciated. Daniel