Excerpts from wcia.com:

Members of a pension system get credits for the time they’ve worked. They can purchase additional service credits that essentially move them from one pension system to another. Those credits will then be used to calculate how much that pensioner receives.

Firefighters outside Chicago who started work after 2011 are not allowed to buy service credit after changing departments. 

The President of the Associated Fire Fighters of Illinois says an Illinois Senate bill would allow tier-2 firefighters hired after 2011 to have the same ability as tier-1 firefighters.

The measure cleared the pensions committee unanimously. It’s headed to the Senate floor for further consideration.