You are indeed asking a question, that can be easily answered with some minor research
K-Line is only used for diagnostic communication.
All the control modules on the PTCAN still use CAN for communication of course.
So while you will not be able to call any diagnostic services or request data from ECU, if you just want to see what is happening on the bus and read the data that is already there you can certainly tap the PTCAN and sniff it.
The format of the ECU messages is defined in the FR and it is possible to turn them on or off.