I've never washed mine by themselves, but I never checked whether that was okay. They will be needed to be waxed again after washing, but I keep mine going by brushing any excess mud off after a trip out when they've dried and then just hang them up for next time. I have the Barents pants, which don't have the softshell part.
They take me about half an hour to wax thoroughly (double waxed from the knees down), which is either a faff or just something you do to maintain some trousers that will last you for years and years. In fact, I'm not sure whether adding softshell is almost missing the point of trousers like these - they're not the lightest, or the most waterproof, or the most breathable, but they won't burn, they won't tear and they'll barely wear, which I'd say less for most softshell I'd met.
In reply to UKC/UKH Gear: these are pretty good for farm work, or if you spend a lot of days outside but whether they're the ideal choice for most walkers, climbers is debatable - a bit hot, a bit heavy and do soak up some water