If these regions are marshy and mellowy than Leopards won't be able to maneuver properly, maybe, even to move. It is very nice piece of machinery, but it is 2 times as expensive as let say Ukrainian T-84 Oplot and 1.5 times as heavy. So, for the same price one can buy 2 tanks with better maneuverability, the same speed parameters and + airconditioning going down to-40C
, which is nice when you drive it west of Oder on a hot summer day ;) In addition, Oplot has 26 power/weight ratio which is unsurpassed neither by German Leopard, nor by Russian T-90. So, if Poland, which has plenty of its own military production, still would be interested in purchasing new tanks - well, why not buy them from Ukraine instead of Germany at a significant financial advantage to itself. Saved money could be used on making Poland a powerhouse of EU or investing into radar system and aircrafts which are always a big deal in the modern warfare.
Don't know, but they are easily spotted!
Who does that? They have enough spots to notice them anyway ;)