The cows avoiding space under a HV transmission line I would guess probably has more to do with inducing voltage/currents in objects below the lines than it does with EMF's. If they get a tingle from voltage gradients in the soil they are walking on they will avoid those areas. This true even when no transmission line is causing said gradients.Is there difference between the original question regarding EMF and the concern of RF from a cell phone? Is RF and AC power generation EMF the same energy? If I'm correct RF is high frequency EMF and has had a higher level of scrutiny because of cellular devices, the EMF from AC power generation and distribution is low frequency EMF.
I believe the issue that created such a buzz over cell phone as well as other radio transmission is RF, that has been studied enough to create safety warnings over high level exposure, to the point of modification of cellular phones, and to be made more public.
"According to the World Health Organization’s International Agency for Research on Cancer (IARC), EMFs are “possibly carcinogenic to humans.” The IARC believes that some studies show a possible link between EMFs and cancer in people." Here is the source quoted:
Here is another study report done by a source more relevant to individuals working around EMF, NIOSH.EMF (electromagnetic field) exposure is unavoidable. Given our frequent contact with wave-emitting devices in the home, you may wonder whether EMFs are dangerous to your health. We’ll tell you what you need to know.www.healthline.com
Based on this information reasonable precautions would dictate that establishing a "permanent" working station would be ill advised.
It also from observation that cows might be smarter than humans in relationship to low frequency EMF emanating from high power AC transmission lines, they avoid hanging around and grazing underneath the 750kv transmission lines run through the north country of NYS.