MMP is not only used in other countries, like New Zealand and Germany, but also in many other states, provinces, and municipalities around the world.
In South Africa, all municipalities designated as either 'metropolitan' or 'local', elect their municipal councillors using MMP.
Most of the provinces (states) of Germany use MMP, including Saarland, which is half the geographic size of PEI, and which has a population of less than 1 million.
For examples of small legislatures, comparable to the 27 MLAs in PEI:
Upper Franconia is another region of Germany, within the state of Bavaria. Only slightly geographically larger than PEI, it elects a small group of 18 members to the Bavarian legislature, using the same 'open list' MMP model proposed for PEI, where voters directly vote for individual candidates, rather than having parties 'appoint' MLAs from their list.
The city of London, UK, also uses MMP (though it's known by the name 'Additional Member System' there), to elect the 25-member London Assembly, part of the Greater London Authority.
There may be more that we are unaware of - we will add more examples here as we hear about them.