On #1 the summary does not seem to match the article. It almost looks like someone with an agenda wrote it without reading the "investigation" report
Power company investigators discovered that the lines had been de-energized at a pole-mounted service transformer. However, incorrect connections at this transformer established a path for current energy from another circuit to travel back (backfeed) through the transformer, energizing the line that the victim had contacted. Tests determined that 2400 volts were present on the line.
In the last one they just guessed there might be a generator involved.
The real common denominator is all of these guys violated safety rules and did not have the conductors they were handling grounded. When you are talking about the fraction of an amp it takes to kill someone that could have been coupled through any utility source, hence the rule
