The filter goes between the phone and the jack. Not between the jack and the modem. There should not be a filter on the line connected to the modem. The phone should not be connected to the modem in any way.
Okay, you have a splitter. That wasn't stated previously. As long as you are using the correct ports on the splitter it should work. I'm not familier with the Enterphone system but you aren't the first one to have issues with it:
It may depend on how the building is wired and how old the Enterphone system is. Apparently there are older and newer versions of the system.
You indicated that this was a new condo. Is the condo a relatively new construction or "new" to you?
Modern interphone systems need to be programmed with the phone number of the suite, this could be a land line or mobile phone number. To get this set up you need to talk to the condo management company.
If your are in a very old building the enterphone system could be one where the system is wired between the Telus wiring entering the building and going to your condo. These older system could interfere with ADSL so the installer bypassed the enterphone system to provide internet access.
Suggest you talk to the condo management company to determine more about your enterphone system.