It used to be that the Palmetto seemed to always get an HHP-8. I think that was due to the roadrailers it often had (I seem to recall that the AEM-7's braking system is somehow incompatible with roadrailers). Lately, however, I've been seeing the Palmetto being pulled by an AEM-7.
Regarding the P32-8's, one of them has been sitting in the MOW yard south of New Brunswick, NJ for a while (I think it's #513).
I took the train from Brig to Zermatt last year, btw! Quite a beautiful place!