Here in NZ the ban on felt soles is into it's second season. It is however not against the law to move a kayak or raft full of water from one river to the next!
I can tell you that in 10 years of fishing the Tongariro with Felt soled boots I fell in twice, both times tripping rather than slipping. Since I changed to rubber soles I fall in at Least once on every trip!, The vibram soles simply do not have the same grip as felt on slippery, bouldery bottoms like that found on the Tongariro, They have proved fine for me on gravel and O.K, but not as good as felt, on bedrock.
All the best.
Mike