We have borrowed uniforms several times from the local departments.  You may end up with summer uniforms in winter or vise versa but we have never had a problem.  Funny Story:  I was transporting a uniform to another theatre when I was stopped in a rural speed trap (I admit it I was going to fast).  As the officer approached the car, he saw the uniform hanging in the back seat.  He said "I'm not going to ticket a fellow officer, get out of here."  I never lead him in any way to believe I was a police officer.  If he had approached from the other side he would have seen a nice lace dress.  I kept my mouth shut, obeyed the officer and left.

A couple of years ago our state troopers donated used uniforms to our theater. We have used them and used them. We have lent them to other theaters numerous times. Along with the priest's cassock, I would say, they are our most borrowed costume items. Yes, badges and insignias were removed, but that is easy to take care of.  There is no harm in asking.