No, actually they aren't. Career prospects for OCI type employers will depend largely on 1L grades, not on what school you attend. Most U of O students, unlike their counterparts at Western, are focused on Ottawa employers. Without knowing the numbers of students from each school who participated, how many apps they submitted, how many OCIs they received, how many offers they received, and how many accepted, a claim like this just isn't absolutely factual. The UV numbers never tell the whole story.
For labour law, firms usually split between union and management. Union-side wouldn't quite be big law -- they tend to be structured as somewhat specialized boutiques. There's a bigger emphasis on fit and demonstrated interest in union-side firms than for big law in general. But the compensation and workplace environment is pretty similar. Management firms can be labour boutiques or might be part of a general, full service firm. I guess in-house is a thing for both, too.
For employment (i.e., employment standards, wrongful dismissal, etc), there's a lot of variety. As in, everything from legal clinics, to sole practitioners, to massive firms.