> Tanks began to fire 120-millimeter canister rounds (in essence, shotgun-type rounds that, once fired, open into hundreds of tiny pieces) down streets from their main guns. The canister rounds blew the trash off the streets and, in many cases, exploded IEDs lying in wait for the patrol.

The interesting part that most people don't think about (and is extremely relevant in a MOUT setting) is the pressure shock coming out of a main gun, which can be deadly for up to 200m:

The overpressure from the tank 120-mm cannon can kill a marine found within a 90-degree arc extending from the muzzle of the gun tube out to 200 meters. (Marines MOUT Manual)

When firing it down a narrow, building-lined corridor, the effect can be far longer, and even without the canister shot it would likely be enough to clear a large section of the street.