TFW application : NAFTA Professional: Job offer letter requirements?

[LesPaul]

Hi,

I am a US citizen who asked to be transfered to Canada and work remotely (btw, not in the same province as the Canadian office). 
I will be getting the official job offer soon from our Canadian branch.
I plan to apply for a TFW Work permit as a "NAFTA Professional"  (I do meet one of the criteria and the job matches).

Note that technically I can work from almost anywhere in the world (restricted by timezone overlaps with a few key offices) so there is little justification that the needs to be in Canada.

Job offer letter : Is there any special requirement other than a normal job offer letter (terms of employment/salary/etc)?  Does it need to justify the position in Canada?

-LesPaul