Here is an overview of the ECMT (European Council of Transport Ministers) resolutions on parking reciprocity. Note that this doesn't apply just to Europe; other member countries include Australia, Canada, Japan, Korea, New Zealand and United States.
At the bottom there is a very helpful list of all countries with details on what parking concessions are provided to holders of disability parking permits - this would be great to review before traveling to another country. For example, in some US states and cities, but not all, parking permit holders do not have to pay at parking meters. This is not necessarily true in other countries, and this resource has that kind of information. It also has links to what office/bureau administers the country's accessible parking scheme.
ECMT Archives on Accessibility for People with Reduced Mobility Reciprocal Recognition of Parking Badges