I don't know the policies for CX, but for UA -- and I think this is industry-standard -- ID90 tickets are 90% discounts off the absolute full-fare ticket for the cabin class. I recall an ID90 for Y from IAD to AMS running about $800 per person. For United, it wasn't even a discount off the standard YUA fare, or other generally available Y fare code, but off the full, wholly unrestricted fare transferable to any airline.

Given that I was looking to travel during the winter, the ID90 actually priced out well above the cheapest confirmable fares. And, as others noted, the ID90 was standby-only, though it was refundable and unrestricted to a given date.

A lot of carriers offer much lower standby fares for their employees (often nearly free in coach), and many have ZED -- Zonal Employee Discount -- agreements with other carriers that let an employee of one airline standby-travel on another carrier, sometimes even in J, for a couple hundred dollars long-haul.

So CX employees, if they're only offered ID90 fares that operate like UA's, aren't getting much of a deal.