Chicago - Using CoachUSA (127th St) for "free" parking at MDW?

I was driving on 127th south of MDW yesterday with a non-FT friend who has lived here forever. We passed the facility of CoachUSA near I-294.

My buddy told me if you take CoachUSA to/from MDW from that location you can park free behind their building for as long as you want.

Anyone ever done this, or heard of it?

They don't mention a rate on their website, only that parking is available. but the r/t from Crestwood (127th) to Midway is $33 whereas parking at the Economy Lot at MDW is $14 a day. So it's not until the 3rd day that you'd come out ahead. But if theoretically you could park there for a week or more, it would represent a significant savings.