No, not really. The engine needed a lot of help from the map designer to make mirrors work at all, and those weren't even traversable without cheat codes, nor were they more than the flex foone describes them as - that's the reason you see one early on in the first level, and very rarely thereafter.
Arbitrarily placed, see-through, traversable, Portal-style portals probably would not have been beyond the skill of the engine implementers. But to make them work smoothly, along with everything else in the game, under the constraints of the hardware on which the game had to run? I find it hard to imagine anyone being able to pull that off, tbh.
Arbitrarily placed, see-through, traversable, Portal-style portals probably would not have been beyond the skill of the engine implementers. But to make them work smoothly, along with everything else in the game, under the constraints of the hardware on which the game had to run? I find it hard to imagine anyone being able to pull that off, tbh.