I had the oppotunity to force open a car door with a manual tool during a training for emergency teams. We used a specialized axe for that and still struggled to get the door open.
The axe provides much better leverage and grip than a Glock field knife. From that experience I think that a Glock field knife (or any knife of similar size) is not up to the job. That does not even take in consideration that the tang of the Glock knife is too short to really give the stability of a prybar.