sparky, i've just been fiddling with some of the plates that VP has done, and i can say that they are just one texture.
the great thing for me, is that it's really easy to simply edit the texture/transparency to get almost any specific airfield/runway shape yo can think of. it's great!
i've also never been a fan of the ruler-straight edges of many runways in the game - barring concrete runways, you never see that kind of uniform angularity on dirt/grass/mud runway edges . they are so easy to spot from a huge distance because of this, and that is completely opposite of what you would expect of a runway during wartime...
the sky is literally the limit with this way of doing it. we need never see another of those perfectly straight-edged runways in the sim again, if we use these, and it's real easy to edit it to make the exact shape runway you want
as for your second question - there are already similar road textures, from quite some time back already, which give a realistic, curved look to roads - the drawback is, as you say, vehicles won't (naturally) run on htem, but you could always set vehicles up with waypoints in FMB, to follow these roads - i've done it on some maps in the past, and it works just fine.
as for railway, i don't know - there was also some sort of work-around technique, i think, to get trains to do a similar thing, but it was much more involved, iirc