It's not a maintenance site, it has a sign saying "Flea Market". There is a left turn lane for it from the westbound lane. ( In Google street view you can see some digging equipment where the jug handle is now. )
One of the buses has heavy front end damage, and the one lying on its side has damage down the length of the exposed side. From this it looks like the first bus swerved across the road and crashed into the side of the other one. One might speculate that someone turned in front of it at that left turn lane, causing the driver to swerve.
I looked at Channel 6 {WATE.com} picture and saw where the wreck was. One bus is between John Sevier Intersection and the Drive IN at the bridge. The other is likely on the other side of that intersection.
Looking at this picture it makes more sense http://www.wate.com/story/27528745/injuries-reported-in-east-knoxville-crash-involving-school-bus This is the intersection of John Sevier where you see the white Ford truck front end and is looking onto Ashville Highway from John Sevier and the view to the drivers left is back toward the river bridge and I-40 and the upright bus.
The bus that flipped from other sources looks like it is east of this intersection just barely or off to the right of this picture maybe in the intersection itself. The river bridge is a flat bridge so no overhead structures like the older one would be visible. This bridge IIRC is about a decade or less old.
The ridge line in the background is the river bluff. There is a small ridge between I-40 and the river. The buses could have legally been going as fast as perhaps 45 MPH and a bus fixing to flip could travel a ways. If I could place the Wendy's it would help but I can't remember. I think if you are coming off of John Sevier it is across Ashville Hiway and slightly right.
If a car swerved it was likely jockeying either coming out of John Sevier or wanting to turn onto it. Maybe someone late for work.
IIRC there is a maintenance road at the intersection itself. The intersection is being developed. I haven't been out there in about a month.