Travellers who have disabled parking permits from other countries may be able to use them in Canada. The permits I am referring to must be official ones, not home-made.
I have used the following terms interchangeably to describe the disabled parking placard:
There is no national-level scheme for issuing and regulating the use of disabled parking permits. The blue and white international wheelchair symbol is used in Canada on the actual parking placard (called a badge in some countries).
The recognition of handicapped parking permits is at the provincial level. In Alberta, for example, you can go to a local registry office and for a fee purchase a temporary Alberta permit.
In practice, few Canadian travellers from other provinces would consider doing this.
The reality is that as long as you are not abusing the system, an official parking pass from another jurisdiction should be quite acceptable, provided it is officially issued and has the universal symbol on it.
If you intend to drive in the downtown areas of the major cities (Toronto, Montreal, Vancouver), and to attend events at popular venues (e.g. sports arenas, concert halls), and where disabled parking might be in high demand (e.g. hospitals, shopping centres), then it would be a good idea to contact the local parking authority to get their advice on whether your parking permit will be recognized.
For most of the country, we are fortunate in Canada in having a reasonable amount of parking and if you can travel at non-peak hours in particular, you should have no problems.
The recognition of the handicapped parking badge from the US is probably covered under a bilateral agreement, but I was unable to find one (yet). In practice, if your permit looks like a Canadian one - white on blue, using the international symbol for a wheelchair - the local authorities are likely to respect it.
This does not mean you should make your own placard! To be official the placard has to have been issued officially and should appear so.
The article Disabled Parking Permits in Europeexplains that holders of Canadian (and other) disabled parking permits may use them in the EU.
When the EU adopted this resolution, the various Canadian provinces agreed to implement it, as the issuance of disabled parking permits is done by the provinces and, in the north, by the municipalities (not by the territorial governments).
Thus, if you come from anywhere in the EU, bring your parking permit and it should be honoured. There are some differences in the exact rights a blue parking badge gives you in Canada.
For a description of how Canadian disabled parking permits operate, and a brief note on how they differ from permits elsewhere, please read this Executive Summary, and in particular the section on Parking badge policies in Canada.
The typical practice in Canada is that if you have an official blue handicapped parking badge with the international wheelchair symbol on it, hanging from your vehicle's rear view mirror, you may park the vehicle in one of the marked, designated handicapped parking spots. These are usually at the main entrance of the building or site you are visiting.
As is the case everywhere, the disabled parking spots can be in short supply at peak hours. If you are concerned, try to research the destination, on the internet or by phone, before going there.
The same general advice applies as for the USA. If you have a standard placard, officially issued, bring it to Canada.