It is true but only for unstable, self-deteriorating systems, like nuclear fission reactors (and other technology that uses unstable elements) or systems using unstable materials, like most organics (sorry, Jimmy, all those zoo animals are dead… I hope). Other systems, that do not incorporate such elements (and this is absolute majority of human technology of that time), can remain relatively fine for decades if not centuries. And all systems that are used by scientists and military are equipped with emergency breakers - it is pretty much the basics of safety measures. Even your personal computer can be suddenly unpowered, left for 10 years, then powered up - and it will be mostly fine. What can we say, then, about military and scientific equipment, that is meant to have several times greater margin of safety?
But it is possible. You simply need to scale it down to personal level. You cannot run old steelworks industry on your own, sure. But did that stop you from metalworking projects like deathmobile?
For this to be true, two other statements must also be true: that zeds are willing to tear it down and that they are capable to do this.
As for “zeds are capable to tear down infractructure”:
Seriously? =) According to lore, whole country lived in expectation of war. Do you imply that several reanimated human bodies is enough to tear down something that is designed to withstand strategic bombardment and (most probably) tactical nukes?
Well, what you are saying of course may be true for civil infrastructure, but this is not an issue - for current civil population this structure is massively redundant, so much of it potentially can be cannibalized to restore other parts of it with little problem.
As for “zeds are willing to tear down infractructure”
Let’s think about zeds motivations. The only motivation they seem to have is to attack the living. So there is important question: what dynamics Cataclysm actualy had?
And judging by state of cities Cataclysm was widespread and instant or near-instant. One moment - everyone is alive. Another moment - everyone is dead. Yet another moment - everyone is zombie. No time window for struggle. It is indicated by comlete absence of any traces of struggle: furniture in intact, firearms are not fired, windows are intact as well (and this indicates that there was no zeds trying to get in or out of buildings).
And as there was no struggle in cities - I see no evidence that there were struggle in labs and military installments: there are no casings around turrets, no broken furniture, no lost or discarded weapons, no broken doors and so on.
And without actual struggle between the living and zeds it does not seem that zeds have any incentive to break apart anything around them, including high-tech equipment.