Note that Znap sets are not available in the USA. So call LEGO and complain. (No, I don't know the telephone number to call.)
These pictures are taken with a video camera so sorry about the fuzziness.
Here it is from another angle.
A close up of one end to show how the Znap fits into the LEGO viaduct.
A Znap beam fits exactly in the gap beween a stud and brick above it.
It isn't physically connected at this point, it just rests in the gap
but the only way it can move is away from the viaduct and that is
prevented by the fact that the track is fixed to both the viaduct
and the bridge.
Thomas crosses the bridge.