Hello Michael,
I agree Alex. Sharing the work will speed up it because this import can only be done manually.
Like I wrote to Alex: can you agree with using the automated import as intermediate phase?
The import has to be done manually because tracks might have an offset at OSM due to a Bing offset and milestones are not mapped on siding, yard and spur tracks.
I checked this at the first try of this import and it didn't cause noticable troubles. The only case I found is a new railway tunnel which was put into service very recently; it replaces the former parallel track on ground level. The reference ribbon is still at the former track at this location. I will handle this section manually and check ProRail's logs for recent geometry changes.
You should split up the data in smaller pieces or create a WMS which serves it. You already have a shapefile, lots of WMS servers/their database backend have an hapefile import.
I'm not familiar with WMS. Do you happen to have a screenshot? Thank you for the suggestion by the way.
Best regards, Jeroen