I have noticed that the new feature in 10.16 does not work as intended with ways other than roads.
Currently, any way type built inside a city will become public owned.
It is still possible to build them as player owned by ctrl placing a lower grade way on top of the public owned one. Once player owned, you can upgrade it to whatever and it will remain player owned.
Thank you for the report - found and will be fixed in the next version.