This looks like the pipeline may have been outside of the mowed ROW.
The photo would certainly give that impression or at the least be on the very edge of the mowed portion. Apparently based upon the photo the Transmission line was crossing the pipeline ROW rather than running in parallel with it. That would raise the question if the utility company even had a locate since they were going to be outside the supposed pipeline ROW with their structure.
I know that when we have built aerial utility’s that if we are placing a pole within 100’ of a Big gas line that the gas company wanted a rep on site just because.
From talking to the Gas Company guys the ROW clearers sometimes get off center as they are clearing ROW.
Maybe that happened this time as well.