It does have a good reception range and the external antenna can even be mounted higher and some coax can run between the antenna and the V572A or just mount the V572A, Antenna and Power Line Interface together in a high place. Though 300' maybe stretching it. In a test. I had one in my attic and I got at least 200' and probably more. With a HR12A Palm Pad and a UR19A Remote.
Now for the possible problem. The TW523 and X10Pro PSC05 are both discontinued. That the V572A uses to interface to the power lines.
On the WGL web page is cautions not to buy the V572 if you don't have a TW523 or PSC05 or a confirmed place to get one.
Though JV Engineering now makes a TW523 replacement and I am sure Jeff will verify the V572A should work with it.
Their XTB-IIR that also has a TW523 feature is listed on the WGL V572A web page.
http://jvde.us/xtb/XTB-523_description.htmAlso Motion Sensors maybe rated for outdoor use but are not waterproof. So chose mounting places with care.