We came across a bilingual website that documents the history of WWII German POWs all around the world.

There is a page for Canada which mentions escape attempts:

600 prisoners tried to escape...in 1947 still 17 [were] not recaptured. 2 were alleged drowned, 1 in the U.S.A., 1 in Mexico and the rest still in Canada.

and a page for the USA which includes a quote about escapes:

Provost Marshal General noticed: "1369 escape attempts were made until March 1st, 1945 but only 12 prisoners of war (6 Germans and 6 Italians) were in liberty to this day."

More details:

• photo albums
• various documents including a postcard written from a German POW to his parents.