Not happening

> "...he incumbent vendor uses restrictive licensing practices that make it prohibitively expensive for the government to fire them and switch to a different vendor."

That's only one part of lock-in. The more expensive part is the cost of migration. This includes replacing other tools or code, and retraining people to use the new vendor's products. It's often thought of as cheaper to just stick with the vendors you (and staff) know than embarking on a migration project with a unknown cost.

This could be dismissed as a sunk cost fallacy, but that thinking is common.