Dan,
Please excuse the delay, but I have used the units you posted the link to before. Around 1990 I think!
I had a tram line, where two trams ran up and down and passed in the middle. One tram was track powered. The other was powered by overhead plus a common rail.
I built a box to control them which featured four EPL drives one for each tram to reverse, separately when it reached the end of the line and two to control the trams departure from the central passing loop.
The points were spring loaded, so each tram passed through the loop in the same way. The isolation of the centre section was interlocked, so both trams had to be there, before either could leave.
Normal LGB reeds and loco magnets controlled most of the switching, but I wanted the system to know which tram was where so that it could be reversed appropriately when it reached the end of the road.
I two mounted block magnets under the 'skirt' of each tram. The track powered tram had them on one side, the catenary powered tram on the other. They were big magnets from burnt out Tri-ang X04 motors.
I used four of those reed switches that you posted the link for, with two mounted either side of two adapted rails. One side controlled the reversing of the track powered tram, the other side the catenary powered tram. I had to mount them really close to the rails and file the tops flat to give good clearance, but they worked well. I used the normally open reed, not the closed ones.
As the reeds inside them failed I substituted ordinary reeds, but used the same mounts. I still have the control box and the two special rails today, although it has been a while since they were used.
They solved a problem for me. That said I did not find the reeds themselves to be that good in quality and I think all failed after a year or two of occasional use. The block magnets supplied were good and I still keep one in my pocket when running the trains should I need to check a reed.
I had planned to do something similar to the above to set different routes for different trains, but mounting the magnet on ordinary stock was not so easy, although my Bachmann Toby would seem ripe for trials!
James