[twobit]

Your lowest cost night vision would be at places like optics planet dot com. I don't know how these "less than $1000" units work or what their quality is. I would however contact your game wardens and see if they can set up decoys on the place. I know here in Texas,for a site with repeated active poaching, the game wardens will usually set up on a place. Wardens have the multi-thousand dollar night vision tools, cameras, and other devices to catch the poachers. Hard core poachers will not hesitate to shoot you, so it is best to let the wardens take them on. Texas wardens put catching poachers high on their list.
EDIT:
You posted while I was typing. Our wardens are State Officers, not county or local. I would contact the higher up commanders if locally you cant get a response. Also here in Texas power line right-of-ways are common across ranch land but are always behind locked gates at each property line. The property owner and the power company have a key. Are your power line easements unprotected by gates? If so I would insist that the power company install gates across the easement at your property lines. Is the perimeter of your property fenced? Nearly all private land in Texas is fenced, but I know some areas of the country that is not the case.