CAN MILEAGEEXPENSES BE DEDUCTED FOR REFREE AT DIFFERENT BALL GAMES?

Yes, if you file Schedule C for your referee business, and if you have a home office for that business, you can deduct mileage to get to and from a game.

The rules are "miles from your business to the worksite", so you would need to have a home office to consider your house as your business location. 

IRS Pub 463

@BLAV if you are refereeing multiple games on the same day, then the mileage from Ballpark A to Ballpark B is definitely deductible mileage.

unless you have a home office, the mileage from your home to the ballpark (or from the last ballpark to home) is commuting miles and not deductible