Yes, my car's ownership was completely changed over to my name in Germany, so I had the Fahrzeugbrief and Fahrzeugschein. I had both, plus the bill of sale on hand plus certified professional translations of them into English presented at the CBSA. In and out in 15 minutes.
The rules are clear: A non-resident visitor cannot sell his imported car here. You'd have to get the title transferred to your name before/upon entry and presentation to the CBSA. The only way I can think of that you can get around this is to give power of attorney (Vollmacht) to a party in Germany and have him go to the department of transport there (Strassenverkehrsamt) to do the ownership transfer to your name. Once you have the 3 documents - bill of sale, Fahrzeugbrief and Fahrzeugschein - along with certified translations thereof, you can go to Canada Customs.
However, the fact that the vehicle is already in Canada, has cleared CBSA as being a temporary import with a visitor and he is driving it around (correct?), may be problematic for you based on my own interpretation of the rules:
https://www.tc.gc.ca/eng/motorvehiclesafety/safevehicles-importation-other-than-faq-1283.htm
I will be visiting Canada with my vehicle. Do I have to formally declare it for importation at the Canadian border?
No. Section 7(1)(b) of the Motor Vehicle Safety Act (MVSA), allows a visitor to temporarily enter Canada with a motor vehicle without complying with the MVSA if the vehicle is used only by a visitor to Canada or a person passing through Canada en route to another country.
Notes:
You alone may use the vehicle.
Any change in your status, such as receiving permanent residency in Canada, may make your vehicle inadmissible and you will be required to export or destroy it.
You may not sell or gift the vehicle while in Canada.
The vehicle cannot remain in Canada longer than the time limits allowed under your temporary entry.
I don't have direct experience with your specific scenario, but IMO, the rules seem to leave some leeway for the agent - in your favour or otherwise. Evidently you spoke to someone with a liberal interpretation of the rules and as long as you deal with that same person when you go with the right paperwork, you should be fine. Another agent may not be as accommodating. The only sure bet is research, preparation, more research and more preparation. If you want to save yourself headaches and not risk being forced to ship the vehicle back to Germany on your dime or have it crushed, I'd look elsewhere.