Okay, don't know if this is going to be much help.
As far as I know all medical practisioners (excuse the spelling), need to be registered locally. I don't know what this entails - the Canadian Embassy/ Consul may be able to help with this!
You/ she need to have all your certificates attested at a UAE consulat in Canada - if there is no UAE consulate the Saudi Consul will do. If you do not have your qualifications attested you cannot be employed in the UAE - except illegally.
Women Dr's and teachers can sponsor thier spouse! This is opposite from all other job catagories, where the male has to sponsor the wife.
Here I stand under correction, but medical/ dental practices have to be co-sponsored by a local partner (UAE National), as is the case with most business in the area. I would suggest that your wife looks for a position before she comes though here. This is the web address of one of the most reputable placement agencies in the area.
They will most probalby be able to help out with regards to practicing locally, what papers you require and as they are an agency are most likley to fight to get you the best salary pacakage (as they are paid a percentage).
Hope this is of some help