I have created a custom tile provider. It is in my repository.
When I save my project and open the .mwproj file in a text editor I see a high number in the TileProviderId-node of the Map-node. Assuming this is the ID of my custom provider. But when I reopen the project file in MW5 the OSM tiles are displayed, assuming it falls back to 0 the ID of OSM. When I change to the OpenCycleMap, save the project and reopen, it is enabling that provider, as expected. Is it intentionally the project doesn't change the tiles provider to a custom provider (when it is available of course)?
Sergei committed a fix.