Eckhard, It is all explained in our proposal at https://wiki.openstreetmap.org/wiki/Proposed_features/3rd_and_4th_rail - electrified=rail is retained and the definition tightened so that it explicitly means 3rd rail. This means that almost the whole worldwide mapped network is unaffected - and the lines that are, I'm happy to retag correctly.
And yes, we are keeping the separate top/bottom/side tag as it is currently - we will need it for 4th rail as well! Hope that clarifies, and hope you can support.
