How to upload centerlines?

It seems like an obvious thing, the ability to upload a centerline polyline (as opposed to the buffer polygon) shapefile to the Facility Locations & Responsability Areas, but nowhere is there any information on how to do it.

There is hearsay in the industry that it is possible, and it seems like it should even be a standard feature, so that ticket responders can view the centerline, not just the buffer zone, when they view a ticket. 

I couldn't find anything on how to do this in the available online Help and will need to contact a human being. 

Loading and viewing spatial (or mapping, or shapefile) data is a very minor but obviously crucial part of the system and it's usually done by a small number of users, so the Help regarding spatial files is small, and could easily include information on centerlines/polylines.

thanks