Russia is 1/6 of the world, a very large country. When it was Soviet Union Russia had a grand army, after fall of Soviet Union old armed vehicles of special forces were sold as junk. This machinery was then converted into construction machinery by Russian constructors.
With those it comes like, passing across a place where the new residential complex is being built a big military camouflaged tank can appear from across a corner equipped with a hoe instead of the gun.
Also, it might be handy in exporting to third world countries where the construction areas are sometimes being combined with a battle front. Such construction machinery won’t be an easy target and would be able to continue digging under the light to moderate range fire.
If you look at some of these machines, its look like armed forces are constructing buildings. [Source En Russia]