So, back in the early 2000s I bought a Bachmann Silver Series tank car. Some years later I dismantled it with an eye to using its parts in a project (ultimately, though, I decided against that). When I did, I discovered that it had been secured together by melting the end of a pin that extended from the inside of the top half of the tank shell. Annoying, that. Had to tap a screwhole in the pin to put it back together. Are they still melt-pinning or have they learned good behavior in the intervening years?

It's not just Bachmann, as many manufacturers do it and they include both road and railway models and of course, it keeps the prices down, eg Oxford Diecast 1:76 road vehicles for less than a fiver!  As you say, a small self taping screw soon sorts it and you can take it to pieces easily enough again.  

Enjoy the fun and of course, the challenge :)

Bill