I used to do this every Monday morning at 08:30 in a telephone exchange by tripping the mains circuit breaker. The engine always started a straight 8 Lister diesel and was left running the building right through to 13:00 or so. This covered the morning peak for telephone traffic.
A telephone exchange, as a piece of electronics, runs on a float power supply, with at least 2 rectifiers to charge a battery, which works as a UPS. Telephone exchanges do not fail very often because power supply is integrated into the design of the exchange. The power supply represents a single point of failure, having integrated redundancy and UPS ensures that problems do not happen. Should power really fail, customers with non urgent classes of service will be prevented from originating calls to preserve power.
Dual integrated power supplies with in built fall back facilities, that work.
Now that all the IT braggarts are exposed for what they are, incompetent buffoons, they have confused knowing a bit about software and knowing a few buzzwords with actually understanding what they are talking about.
Perhaps actually looking into a bit of electrical engineering and being ever so humble might well be the order of the day.
And the comment about disaster recovery, I worked for an FM company here and we tested out our DR plans every year. No one was allowed help from their colleagues, they had to follow the documentation and correct it if any errors were found. The trial simulated a real disaster and the guides were to enable anyone with a modicum of IT knowledge to recover the systems under test. Users were involved too, they were shipped in to test fully functional systems and sign everything off.
In fact, when relocating mainframes, I used to implement the DR process at the client site and use that for the system transfer. I moved 3 mainframes using this technique and every one went without fuss or problem. Why was this, because the DR system had been properly tested, was proven to work in annual trials and was relatively easy to implement.
I haven't named the company, as it may cause embarrassment to their competitors.