I have a couple Thule racks - the rails are 10mm in diameter.

I DON'T have any Ortlieb bags but their site indicates that recent models have oversized clips with reducers available to fit them to 20mm, 16mm, 12mm, 10mm and 8mm rails depending on the the model.

So probably. The Ortlieb system is pretty well supported.

I'm using Arkel bags on Tule Racks myself - that's another system that's very well supported.