YES ... but ... that's only one option. And it's not just "PEN" problems. There are TWO other issues to consider here:

1. What if I said that "diverted earth currents" are not limited to PME, but possible in ANY system with main protective bonding?

2. The harmful current n may not come from a protective conductor, but a live conductor, or even a telecomms/auxiliary conductor?

Worth remembering that we don't need Amperes to kill, just mA !

Are we talking electromagnetic induction and conductive coupling when it comes to telecoms ?

See I told you there is no such thing as Safe Isolation. No one has mentioned borrowed neutrals?

So I was taught, and teach, when testing rubber soled shoes, no metal jewelry (tape if unable to remove for religious or sentimental reasons), don't lean on anything, one hand in your pocket and don't touch the shiny stuff! And remember there are bold engineers and old engineers but very few old bold engineers! 

My 2 pole voltage tester issued to me in the Post Office was a Drummond Test lamp known as a tester 133A. Standard issue until an engineer used it on a lift and managed to pull in a relay causing a contractor to energize and the lift to move causing a near miss accident.  Testers withdrawn and ordered to be destroyed and a a Martindale issued as a replacement.

The years roll on and I leave the Post Office. Later an engineer had a 2 pole tester hanging around his neck working on an isolated machine leaning inside the machine  manged by some fluke to short a power factor capacitor, with a broken blead resistor, and discharge the capacitor in to the centre of his chest causing him to convulse and wet himself. Big inquiry and back comes the Drummond Tester to be used to discharge capacitors

So would your safe isolation procedure would have picked up the charged capacitor waiting to bite you?

As Inspector Clusoe said, "always expect the unexpected".

JP

All RCBOs off, main switch on.

The reason for the issue in the previous photo. 

I posted these photos a few years ago,  they are classic examples of unexpected issues that are potentially lethal. 

AMK said:

Are we talking electromagnetic induction and conductive coupling when it comes to telecoms ?

Yes, but not limited to telecomms, inductive and capacitive coupling can also occur with power circuits ... also in three-phase networks (or installations) because isolators don't always disconnect the Neutral (esp. TN systems), if we isolate, then there's broken neutral in the supply to the board we're working on, could mean a nasty voltage on the Neutral !!!

There are LOADS of ways we can be side-swiped by "accidental, unintended, or unforeseen" voltages and currents.

John Peckham said:

No one has mentioned borrowed neutrals?

or broken ones upstream of  the circuit we're working on ... and I'm not talking about PEN either ! It's not always a requirement of BS 7671 to isolate the Neutral, BUT that doesn't mean it's always safe to touch, just like the GNYE conductors out there !

Chris Pearson said:

It should not be possible for the installation to become live if locked off and the key is in one's pocket (electricians' padlocks are sold with only one key), or perhaps the main fuse(s) is.

What do you mean by "should" ... and I'm afraid, sadly, it's an incorrect assumption that a given installation can't become unexpectedly energized, if "properly isolated" and locked off. It should,. however, be designed so that the risk of that happening is kept to a minimum of (hopefully) very unlikely events.

I assume that picture(s) is in a domestic dwelling?  Are they DP (Dual Pole) RCBO?  Single pole with switched Neutral will also suffice.  I have heard of people especially in a house having the Neutrals shared and then getting a back feed.  I always try and advise that RCBO DP or SP with switch Neutral are used. 

Did you find what caused the issue in this picture?