Which raises an interesting follow up question: If the narrow street is paved (which they tend to be), are the mines HIP? NRBH at the moment....
"B
31.142 MINES: All mines set up in a hex that contain ≥ one paved Narrow Street hexside must be placed on-map revealed (i.e., with the type and strength of that minefield displayed) unless all the Narrow Street hexsides of that hex are also Crest Line hexsides formed by lower-Base-Level hexes. The removal of such revealed mines as per 28.53 is NA. Mines in
either of the two hexes common to a Narrow Street hexside (or in both such hexes, if one contains A-P mines and the other A-T mines) can possibly affect a unit using Bypass along that hexside; however, if
each such hex contains mines of the same type but of a different strength from that in the other Location, only the
higher strength can be used to attack the Bypassing unit.
[EXC to both: If that hexside is also a Crest Line hexside, only the mines in the lower-Base-Level hex are used]."
von Marwitz