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I got caught in a wet descent (and ascent) on Furka last august, definitely sketchy but do-able with swissstop black prince pads.
While not on par with aluminum rims in brake performance in wet (for mountain climbing only wheels I would spec shallow Kinlin's) all-round I'm pretty happy with the LB grooved rims.
edit: I live in Belgium so the terrain is not really over demanding for brake carbon rim brake performance, even in Ardennes or Eifel regions.
The more expensive option is in my experience a bit better in the wet. The non basalt is fine though.