TraX inner bags in BMW GSA panniers?

[AdamA]

I have searched but can't find anything on the subject, so if I have missed it, forgive me and please point me in the right direction...

Do the TraX bags:
http://www.motohaus.com/acatalog/TraX_Innerbags.html
fit in the BMW ally GSA panniers?

I'm guessing they are a lot cheaper?