Based on the following reply on KS, it seems that terrain items are to scale, and I would assume the same for the mats, though I know it is dangerous to assume:

@Michael, the artwork we commissioned for the terrain packs has been specifically asked to be in scale with the ships (1:1000). This is of course very important when buildings and similar items appear. The photos featured until now use the Wings of Glory mats, which are painted to represent an aerial view.

This was given in response to the following:

How does the terrain scale in relation to the ship models? In the mock-up you have shown in the latest update, the Forts look tiny, like seen from a larger distance. This would mean that the ships would be way too large in comparison to the terrain (the same seems to be true for the islands which can be build with the first terrain pack). I guess the difference in size will not be as huge as when using WoW mats, but it might still be enough to break the immersion and give a game a abstracted feel.
Can you show us a photo with a ship and some of the terrain (it does not ned to be a full production copy value, a simple printout of a preliminary artwork would be sufficient) so that we can judge the scale of the terrain better?