Well, more often than not, you know that you're dreaming even before the RC, at least it's that way for me, usually. The RC is just confirmation of what I'm already assuming. So in a way, the dream does initiate the lucidity.

I can recall one distinct event where an RC clued me in first, though. The day before I had been talking to someone about how light switches don't normally work in dreams, and in my dream I was flicking a faulty light switch. After a time I realized that I had recently talking to someone about this and became lucid. I woke up shortly after, though.