I do not ski at Catamount or BE, but saying that is "not happening" is just guessing without having access to the numbers. They probably saw a reduction in visits that was well beyond the normal patterns.
Your hypothetical was that they are only getting 10% of normal visits (i.e. 90% of the people stopped skiing). BG saying that isn't happening is a pretty damn good bet. You may see a drop, but 90% is just ridiculous... Plus you haven't even gone through a weekend yet with this hysteria in full swing so you don't even know how much your business has dropped during your peak times.