I don't know of such restrictions on the amount of MMJ that a person can purchase or be in possesion of here. In Canada, it seems that the limit is set by what ever the patient's prescription stipulates and if none is stipulated, it seems to be up to the patient and the dispensary to arrive at an amount.

For example, a B.C. resident has received a Health Canada licence to possess 60 grams of marijuana for daily medical use, allowing him to legally grow as many as 292 marijuana plants. He doesn't smoke it, but makes medicinal products from it.

http://www.canadianmedicinalmarijuana.com/?p=226


More info on medical marijuanna in Canada:

The Canadian Federal Gov't will implement a program in the spring of 2014 that restricts such grow ops to commercial enterprises. Word is that the current legal operators will be able to obtain that designation fairly easily via permits and licensing.
The reason for the change? The feds want their share and will try to get it through inspection fees, licensing and taxation. It is unlikely to affect the price as more growers will likely climb on board under the new program and that will further saturate the market.

The following recent news article highlights a community that is a suburb of Vancouver, B.C. (West coast), with a population of around 100,000. Like many such suburban communities, it has around 600 legal medical marijuanna grow ops (and probably an equal number of illegal ones).

Complaints about medical marijuana grow ops:

http://www.cbc.ca/player/News/Canada/BC/ID/2401933471/

After it is all said and done, there is apparently so much marijuanna growing (both licenced and unlicenced) going on that the emphasis in enforcement of regulations and subsequent prosecutions has mostly shifted to illegal street marketers.
Even then, convictions usually result in minimal sentences (if any) and a fine; which is essentially seen as the cost of doing business. Hardly a deterent.

The police tend to not get involved with anyone who has a licence to grow, transport or possess because the Crown Prosecutors (your equivelent to the DA), balk at bringing such cases into the court system unless a very large, blatant offence has taken place. In those cases, basically the grower looses their licence to grow, may face a bit of jail time and the usually imposed fine.

So how available is marijuanna here? I live in a small rural town with a population of around 24,000. A short stop into any coffee shop, will get me into contact with a supplier in minutes and the stuff in my hand a few minutes after that...all under the nose and observation of the police, who would likely also be in the coffee shop. They truly aren't interested in small amounts exchanging hands and prefer to go after the bigger fish...which they do.

Our community's most recent drug bust in July netted over 500 plants from a sophisticated under the ground grow op, cash, guns and stolen property. That was over a month ago and those charged with various related offences were released with a promise to appear in court some time in October.
It's all a gaff .

With love, Erika