I think the PS1 version was sort of based on the Windows version, although I'd have to check that. It shares the high-res graphics and level list (for the most part – it doesn't contain the special levels, one iteration of We all fall down, Tricky 21, Tame 17-20, and Wicked 2). Anyway, you can certainly have lemmings walk over the top of a level, which I find very annoying (Mayhem 23 is suddenly a lot harder!). They also disappear and reappear when their feet are within a few pixels of the top, and there's a glitch in the builder skill when you reach a few pixels from the top – any step placed will just disappear and the lemming will immediately become a walker. This is noticeable in Taxing 5, and someone made a video on youtube complaining about it. You essentially have to stretch the bridge in order to cross from the top of the metal to the bars at the top, although this is actually slightly more difficult than it is on any PC version.
Another glitch is that a builder will always turn around at a wall before you have the chance to bash through it, and you have to time your bridges so that he places the last step to connect with the wall and transitions to a shrugger, which stops him from turning round straight away.
What levels would I go to to test these glitches, by the way? Particularly the sliding glitch and direct drop. I would also quite like to confirm whether they work on the Mac.