I don't think this class of customers care much about OSS. Vendor costs are an accepted business expense, passed onto customers, funded by tax dollars. Why would these big players dance around trying to get what they need from OSS when there's this "tried and true" vendor already proven.
Sure they're greasy, unhelpful, extorters... but hey... "this is big business baby! You gotta tango with the big boys if you wanna play ball in this field, bucko" :_)
All over the world? If not, then there's the replacements, although I'm sure they're not FOSS.
What the hell is security?