the only problem, if one wants to call it that, you may experience with used RC track is if it was in the sun for prolonged times. The black of the track starts to get bleached and it has a gray appearance. The track is still fully functional but it just looks faded. It does not bother us at all but to some having things look new is important. I personally buy used track, we need so much to make a proper layout that I could not afford it at $5-ish a piece.
As far as other brand, as Gordon said it is unique to the company. You could use any G scale plastic track but it will not clip together with playmobil plastic track. We use both brass LGB track for our old trains and the plastic track for smaller loops within our dioramas. We will soon use the brass to plastic connectors that Geobra made to try combining them. The RC trains go on brass track very well and have the klickity klack sound of a classic train that you do not get on plastic.
i think if yo saw the way that some of the stuff we have gets played with you would know straight away that a little bleaching would not be chief amongst our concerns

. i've actually thought about painting the rc track anyway.
right now, i'm facing a problem of availability of track and, then, the cost of the track new when it does become available again. 50 bucks for 12 pieces is tough to stomach, as you yourself note. of course, when one starts looking at the expense of brass track and train stuff in general, it doesn't seem that high, i suppose.
i like the idea of true train grind. right now, our only squeakiness is coming from the tipper cars and it's a bit annoying rather than, say, endearing!