Part of it depends on how you define "open." Not much of what I've recorded over the last 2 or 3 years is open in terms of I can just walk in and setup, but all of it was done with prior approval that I negotiated well in advance. You'd be surprised what you can get approval for if you are willing to put in a serious amount of effort and negotiation beforehand. Doesn't always work, but it's better than I expected.