I had a case where the arb signings put me over budget. The simmy automatically raised my payroll budget by $3M and took $1M from 3 other areas.
Here is the message I received: Due to the recent arbitration hearings, it looks like we're forced to raise our player payroll. In order to do so, we had to trim a little bit from the other budgets. I hated to make the changes without your approval, but we weren't left with much choice thanks to the arbitrator and the somewhat questionable budget that was originally set. Bottom line -- we had to increase player payroll by $3,000,000.