I can speak to the trades. A couple of years ago we did some work with the Centre for Canadian Language Benchmarks to benchmark the examination requirements for someone to be certified in the red seal trades. We found that on a benchmark scale of 1 to 12, they came in at roughly the 5 to 6 level. So on the scale of 1 to 12, according to the Canadian language benchmarks, passing the exam requires about a 5 to 6 level.
On October 8th, 2009. See this statement in context.