It's open to all V3 users since January, but we're holding off on posting ORC subs. on the shop page until 3.06 is final (see below for why). In the meantime, you should ping FuzzyBro to activate ORC for your account if you are a 3.0 licensed customer. This will allow you to run estimates on ORC before you pay for render credits and start a cloud job.
To that end, we still need to update Octane Bench w/ Pascal (now possible with 3.06), then fully migrate ORC costs/estimates to final 3.06+ OB/hr (including AS estimation when used). After this is done, we will place ORC onto the public subscription page, and allow credits to be purchases in OB buckets/hr, based on the pricing we shared at GTC16.