In the 1986 book "Railroad with 3 Gauges The Cincinnati, Georgetown & Portsmouth RR and the Felidity & Bethel RR" by David McNeil, the CG&P started out as a 3' gauge steam freight RR and allowed 60" (5') gauge city street cars on it's ROW (dual gauge). Later the CG&P standard gauged and became an interurban.
There are only three photos (two from the same location - one zoomed in) in the 560+ page book that show tripple gauge track, but the one photo is in the "Carrel Yards in 1902" and the trackwork is amazing.
The tripple gauge (from pic on page 84) has a common rail on the right. The standard gauge rail looks like a guard rail to the 5' gauge. A 5' gauge left hand turnout is crossed and immediately the 5' gauge switches common rails. The next left hand turnouts are for either the 3' gauge or the 56.5" gauge.
If you can follow the description, the left hand of the four rails is the standard gauge rail. the next rail is the left had common rail to 3' gauge AND 5' gauge. The next rail is the common rail to the 3' gauge AND standard gauge. The right most rail is for the 5' gauge. The distance from outside rail to outside rail is about 7'.
Although hard to see (the photo looks to have been pasted onto a page with text and the the entire sheet photocopied), the entire mess has trolley wire overhead.
The definitely could not run 5' gauge with either 3' or standard gauge!!!
If I can gain access to a scanner, I'll see if I can post this photo.
The other pic (page 90) shows a triple gauge switch on top os a steel viaduct. Three gauges to the right and two to the left.