LOL. You know, now that you mention it, maybe
I should just run these Conti Winter tires in the summer and stick with the grand touring Balloons through winter. Why? From driving yesterday till today, in dry, icey snowy conditions (which is a world away from wet, sticky snowy conditions), I can discern no difference that the Conti(s) are any better at gripping, stopping than the Cooper LifeLiners gt balloons.
As Deputer said, these cars are one of the worst to drive in when the temps are low, ice is everywhere, and snow is coming down steadily. Of course, you already know that. Guess that is why these European e39 owners all have either Volkswagons/Passats, Audi(s) and/or other front-wheel drive cars/SUVs for their winter vehicles.
You rarely, if ever, see an e39 at the ski and/or mountain winter resorts. Last one I saw, when in my wife's front-wheel drive ZTW, was about 4-5 years ago, and that was in relatively tame (incline-wise) Oberau/Garmisch. That e39 diesel 530 wagon was totally decked out in those fancy chain-like kevlar (or whatever it is made out of) 360-tire wraps.
As a fellow owning e39 German friend said to me once, an e39 and climbing go together like lederhosen and wine.