Gary,
I'm by no means an expert on various fog machines, but I do know that glycerin-based fog fluid is not an oil. It is water-based - a totally different type of substance.
I also do know that glycerin tends to be sticky as it dries. Not sure how much residue is produced at the concentrations of glycerin used in these machines, but there definitely will be some. It might require a more difficult type of cleaning to remove, as compared with the oils we usually have to clean periodically from track.
I'm also not sure about the effect of the water vapor produced which will eventually condense to liquid water.
But, if you just use the machine sparingly for a little fog effect during a short photo session once in a while, there might be no problem.
I would also do some Google "research" on various fog machines and their effects on people and surroundings. I'm sure some people will be sensitive to it, just as some have problems with our regular smoke fluids.
Jim