I would consider IB’s spread orders held on their server an option dark pool as it is not posted to a COB and not part of price Discovery outside their system.
I would not consider an option held upstairs as a dark pool in the traditional sense because 1. Access is internal 2. It still has to come down to fill and then it may not if the market has moved 3. The market that would fill is away from by the time they recognize it
Yes - this is the idea that I think I was struggling with..."Hidden" simply feels like a bit of a misnomer when the order type is of the simulated (i.e. held-on-IB-servers-until-marketable) variety...because if I'm correct in what I wrote in my previous post (that if I'm "Hidden" with a Buy 5 x $1.15 Bid, I won't get hit by either a 5 x Market Sell, or 5 x $1.10 Limit Sell), it really just acts as a kind of stop limit, and requires a lit Sell order at exactly my Bid in order to trigger....
IB definitely internalizes orders and regular ones as well not just "hidden". They fill anything they can and even take the spread from both clients. However, as Robert has already said, I can't see the point of your hidden order. (If you attach an order to an alert it will stay at IB until there is a trade at your price - which submits the order by triggering the alert)
FWIW I asked IB this and they said they don't match hidden orders up against each other (even when they're both submitted by IB clients and hence could be matched up internally, which would seem like common sense, but who knows). If I'm understanding correctly, both of the things you describe -- a 'simulated' hidden order, and an order tied to an alert -- would essentially function exactly the same way...?