Are you sure those are Blazers? They look more like Tahoes, and they’re common as first responder vehicles, which the one on the left appears outfitted as.
I’m also not sure that’s a real Hummer; something looks off about it. There are companies that sell kits to make other vehicles look like Hummers and I think this might be one. The current Blazer is 76.7" wide and 67" tall. The Tahoe is 81" wide and 75.9" tall. The Hummer H1 is 86.5" wide and 77" tall. Ten inches would be pretty noticeable side-by-side with a Blazer I would think. Even if these are Tahoes, a real H1 is a bit taller, and I think these look a little taller than the Hummer, which again makes me think it’s a kit.
The H1 remains a ridiculously wide vehicle (while lacking interior width for occupants from what I’ve read) for civilian purposes. The height was tall, but also not out of the range of normal compared to work vans. I don’t think I would worry about height clearance in one except for very low parking garages.
You might be right about the Chevys not being Blazers.
I don't know why the police would have a kit Hummer. The interior looked like a real HUMVEE, with tiny seats, a wide partition down the center, and a spartan dash and instrument cluster. It even has a big, circular hatch in the roof.