I’d also settle for releasing 3D models of out-of-production parts so they can be 3D-printed by enthusiasts.
Story time: in my second-gen Mazda Miata, I closed the centre console lid on a piece of cardstock by accident and it snapped the plastic piece that latches the lid shut. The part previously sold for ~$10 but they stopped producing it as a standalone part at some point and the only way to acquire it was to buy the $100 centre console lid assembly.
Have you called the LTB to see if they consider removal of a property management company a “removal of a service”?
My hunch is that it’ll be an uphill battle for you at best. The landlords will have a reasonable case that they are simply changing service providers from a company to themselves, and as long as the property is still maintained and repaired in a time frame that is compliant with the RTA, my hunch is that you don’t have a case.
Do keep us updated, though.