CONFIRMATION - ARTILLERY CLEARS MINES
PIC 1 - A selection of German arty spotters of all calibres (81mm to 170mm) target the Russian buried AT-minefield at the crossroads. (They can't see it of course but we know it's there for the test)
PIC 2 - After all the barrages end, the Panzer II's move straight through the minefield without exploding any, that's why the mine icon hasn't appeared on the map. Conclusion -the arty must have cleared the mines.
PIC 3 - The view from the Russian side shows their mine icon is still there and it looks quite normal, there's no way to tell it's empty and harmless.
(noob note - the Russian infantry in the woods mis-identify some of the Pz II's and think they're Pz III's, there's extreme fog-of-war for you, very realistic)
PIC 4 - HOWEVER in this second test below I only fired an 81mm mortar barrage (total 150 rounds)
but the minefield remained active and immobd the first panzer that tried to cross it, and the mine icon appears. (The rest jammed on their brakes as soon as it appeared and plotted around it)
CONCLUSION -Arty clears minefields but you need lots of medium or heavy-calibre shells to do it, so it's hardly worth bothering in most situations.
(PS - i'll add this post to the Mine Kampf thread in the tac forum)