Mostly no — and that's by design. Digital DJ Pool is a discovery tool for new, independent music: the fresh tracks labels and artists are actively pushing right now. Older catalog doesn't need that promotion, so it doesn't come through the pool.
So this isn't the place to dig up a classic from years back. It's where you find the next record before everyone else has it. Anything you download is yours to keep and spin forever — so the new finds you pull today don't expire.