Kinda' removes the doubt for me, obviously there are chemicals that can affect track, quite possibly in a negative way. A couple of quotes from the above references.
One ingredient in Magic Eraser (formaldehyde-melamine-sodium bisulfite copolymer) contains the word "formaldehyde" in its chemical name. However, this ingredient is not formaldehyde and poses no health or safety risks. (Think of this name like "sodium chloride", which is table salt. Sodium by itself can be dangerous, but sodium chloride - salt - is safe.)
I don't know what the actual effects of formaldehyde-melamine-sodium bisulfite copolymer are on the track, but it's likely that it's not good.
The crux of the matter is no, the Magic Eraser does not contain harmful chemicals. It is made of melamine. The PH factor of the pads is between 8 and 10, which is alkaline enough to cause “base chemical burns”, but that is pretty mild. The Urban Legend page says “for example, Milk of Magnesia has a pH of 10, and soapy water has a pH of 12”.
Truthfully, certainly for steel track, anything that has a PH that significantly deviates from 7 would give me pause as far as using it for cleaning. The myth that it can't leave a residue seems to be dispelled.
While the PH of stuff like Isopropyl Alcohol is not neutral, it evaporate so quickly as to have minimal effect, and it leaves no residue.