Can union bumping rights be used when there are vacant positions available?

I work in the criminal justice field and my department has been experiencing budget problems because of the economy. The department has issued an abolishment of position which has created several bumps to have taken place. The person who holds the abolished position does have more seniority than I by several years, but we work within the same division/clification. That being said, is he able to utilize his bumping rights when we currently have three vacant positions within our division or should he have to take an open spot? I have read the our collective bargaining agreement and it does not address either way what happens if there are vacant positions available. Please note that this process was forced by our union steward to take place.