That's interesting. With the exception of retirememt contributions, I've never worked at a place that withheld any benefits. I have had trial periods where I got a raise after proving suitability for the role.
I don't think (most) benefits are withheld in canada (or in europe). The point of probation there is to provide an initially relaxed (labor protections wise) 3~6 months "at will" to check for actual suitability since you don't really know whether things work out until work's actually been done. Breaking the relationship later is a more involved and expensive process and the thinking is that within the early 3~6 months the employee would know whether they want to stay, and the company whether they want to keep.
agreed. I got my benefits (stuff that the province doesn't cover - like perhaps some $$ prescription or eyeglasses) day 1 of new job, and probabtion is 6 months (i.e. can be let go without the whole "improvment plan"). Other places will have shorter probation and maybe full benefits after 30 days
edit: I am in Ontario and I know a guy in the medical feild that had a 1 year probabtion