I can say from experience that in the U.S., the procurement people are definitely incentivized to look for solutions built on open standards and open source because of the ability for the government to have the option to not ever have to upgrade again, but to continue servicing this specific procurement (and this specific version) forever and ever and not be beholden to a specific vender or solution provider.

I've even seen cases where one company will sell a solution into the government and lose the maintenance contract the next year to some entirely different company who underbid the original provider -- and there's minimal slowdown in technical execution because the entire stack is open to some degree.

The government is starting to develop an allergy to vendor lock-in because of this.