So far with the spoilers we have it does seem that Charla & Mirna are taking advantage in getting off of transportation early. Whether they go as far as Peter & Sarah and get escorted through customs remains to be seen. THough it would explain some of the sizeable leads they have in the locations after arriving on a plane.
And going from what I could see of of old copies of season 5, they might have then as well.
I personally have no problem with it. Its not cheating, it isn't binding the rules. Just as senior teams can legitimately save money on the race by takin gadvantage of their age at certain sites, Charla using her legitamte disability to help her team is perfectly fair (and I am not a fan of this team, well not Mirna anyway).
I have a much bigger problem with needing a "Doctoro" and hold the boat for me, or get me booked as a priority standby for medical reasons compared to people on standby ahead of you (both occured in season 5).
But they do bleed considerable amounts of time in running and walking tasks. And her "special" shoes are only really going to be effective (if at all) on solid level surfaces (pavement, concrete, ect). Fields, dirt roads, ect are going to slow them down a lot.
Also the race never lets teams when arriving at the final city get a custom advantage (at least in previous seasons), the regular legs, yes. Final no. So I see that being a serious issue for them on the last leg. If they make it that far