Current California DMV rules prohibit issuing a vanity plate that matches patterns from sequential plates. When new sequences are used, there's potential for overlap, but I suspect not many people would have picked vanity 'numbers' that match the patterns. Initial zero is unused, but probably still reserved.

You can get an 'environmental plate' issued with a sequential number though, which I believe is less than the vanity plate fee.

And there's some rules around using historic plates on historic vehicles.