I work on site.
If you have a trade you need to join a union, clac is a union formed to bust unions.
As you said you just want to be a labourer, then try applying with PCL, kiewit, Flint, denegold, northern crane, North American and K2.
What your looking for is companies who have contracts on site.
You also need tickets, just the basic stuff depending on what your going to be doing, h2s and csts. Call up some of the places in nisku that offer courses. They are like a test you take for a few hours on computer.
Camps are dry, means no drinking no drugs, there is money to be made here however often jobs are given to a friend of a friend. Just keep trying and be ready for keystone xl.