Running long-hood-forward does decrease visibility, I know from experience. I realize there's a safety factor in the event of a crossing incident, but it also makes seeing signals, crossings and the track ahead more difficult. Take this little GP20ECO unit for example. If this engine were set up for LHF operation, the engineer wouldn't be able to see more than 10 feet or so of the track in the first picture. Now imagine a big SD60, or a GE Dash-9 or EMD SD70ACe with those big flared radiators, and your "forward" visibility drops pretty quickly.
I don't have any statistics in front of me, but I'm willing to bet that train-crew fatalities haven't increased since the introduction of safety cabs. And I'm certainly not going to trust a camera, even a VERY expensive one, to "see" for me. A "slight" issue with the monitor's color is all it would take to cause a not-so-slight problem when reading a color-light signal.