Prolly not many Linemanblood.... the C4 is primary used in Canada the bucksqueeze is here stateside... I climbed with a pile of Kanunks that had to use the previous versions of that when I worked up there... they hated it but were required to use it... me and the other 'mericans got away with out it cuz we were contractors... there were many of those cats that could hike a 90 in those things as fast or faster then some 'mericans could with a straight stap though so when it can to 'hiking I never really saw a difference really... don't know it the Kanucks were cheating it a bit or not... I know it can be done but whether or not the fuggin thing will catch ya if ya kick out I dunno...
I personally have tried the C3 and am required by my utility to use the bucksqueeze... they both suck if ya ask me...
but I've either freeclimbed or hitchhiked my whole life so all of it sucks as far as I concerned but thats antoher thred... maybe some of the New England lineman have done both especially the boys that are outside hands...
This is what we use http://www.jelco.ca/en/product_detail.php?id=2 If any one has fallen & was using the equipment correctly in Ontario they would stop us from using it & make us find something else that works. Edge was pretty much bang on about what he said regarding the pole choker.