Can you add Hikvision CCTV cameras to a Hikvision Intercom monitor?

Yes.

Hikvision CCTV cameras can be added to an indoor station thus allowing remote viewing directly from the indoor station for added security.
A typical Hikvision room station can have up to 16 cameras viewable – one at a time.

For a guide as to how to set this up, please see attached:

Gen1 Intercom – Tech_Note_Adding_IP_Cameras_to_To_Room_Station

Gen2 Intercom instructions below:

Step 1- Get SADP tool to get the IP address of the NVR.

Step 2 – use IVMS4200, add the room station to IVMS. Then add as per screenshot below:

Otherwise via Intercom monitor:

Settings > 2 Icons on right (Configuration) > 3rd icon (device management) , Click on + sign and enter IP address. Port 554. username / password is the details of the camera.