The eastern "fortifications" along the border were meant for surveillance of the border and for preventing unarmed people from egressing. Thus they had very little capability to actually help in a defence (there were some fortifications that would classify as "pillboxes" along the border IRL of course, but hardly enough to warrant a counter). Where you would have pillboxes would be near the installations that were supposed to house the main communition and HQ nodes at army level and above on both sides (COMNORTHAG, COMCENTAG, COMAFCENT, COMBALTAP for NATO for instance, and the various Front and TVD HQs for WAPA). The austrian and swiss militaries were really the only ones sold on permanent fortifications as a mean of territorial defence against overland attack.
RE Mines:
The only mines that were removed were of the SM-70 type (a sort of East German equivalent to the Claymore). For various reason this type of mine had gotten an execrable reputation in the west (probably because they were visible to the naked eye, since they were mounted on the border fence) and the W. German goventment put it as a condition for loaning the GDR further money, that this type of mine be removed (1984). But other types of mines (typically traditional dug-in pressure-plate designs) continued in use. You could of course argue that the border fortifications would be better represented by Obstacles instead of Mines, but I digress.
RE laying of Mines.
Tazaaron is right. Mines (apart from the supply immediately available to engineer units) would typically be on the "critical item list" almost from the get-go. The problem here is, that the game doesn´t track Mines (apart from artillery delivered ones), which means that the mine-probability should be also take into consideration, that the number of mines available will be limted.