The HT lines normally get aircraft following roads or rivers or in limited visability. Not so much on landing, you are correct.
The Flying in the Wire Environment course that the HAI Hosts is taught by Utilities Aviation Specialists. They teach that course 50-100 times a year to operators all around the world, but primariliy in North America, Australia, and China. The US national guard has hosted the training on numerous occasions.
The army has their own training...
As a side note...We yanks have trees much taller than 30'.
Here in Oregon 300' is not at all uncommon. Douglas Firs which are about as plentiful here idiots on Just Helicopters reach about 120M.