There are some field which are strictly regulated like Which I know are Law, Social Work, Nursing, Medical which can effect the local population services standard. They want you to have local knowledge about standard, level of satisfactions. I was working in insurance co. there for 18 years when I joined a company here, they advised me not to talk to clients until and unless you pass an exam and Alberta government grants you licence to practice you insurance profession, therefore, I wrote an exam and now I can practice my profession, They need one to be competent enough and highly skilled in their field of work and knows the local rules and regulation. apart from licence every insurance professional has to attend 15 hours of training every one has to submit every year the detail of 15 hours of training to maintain licencing and applicable to all from Agent to CEO/President of company.
My Wife was social worker we never heard of licencing for social worker in our native country, but here they need to be licenced, they have set a very high standard and level of Social Work services and one need to be licenced and every year licence can only be renewed if you attend courses, must practice your field otherwise it will be suspended and you can not work in your field of profession.
You must check every profession requirement as some are licenced and some are not, those profession which has contact, working directly with human/clients or public it need licencing. in some cases you grant licence if you have enough educational requirement some or many.
Therefore, credential assessment does not grant you licence to practice in your field of profession. it only ascertain at which level your education has in Canada and then you can apply separately in relevant licencing authority. Like I got my insurance licence from Alberta Insurance Council after passing the exam and my wife got her Social Work Licence fro Alberta College of Social Work.
Trust it work.
We're planning to go there end of March. 
