Hi Teia - I don't think "I'm calling as regards..." would be correct, although no one would mistake the meaning. But you would say, "As regards the lunch break, no employee is to leave the office before 11:30."
However, and remember this is my opinion only, both phrases are stiff at best and pretentious at worst, and lead those who indulge in them gently but inexorably to the dreaded "irregardless."