The surrounding tissue does not receive a dose in the hormetic zone. The hormetic zone is where a low dose has beneficial effects, but there are no such beneficial effects to surrounding tissue from low dose exposure. I'm not aware of any beneficial effects to healthy tissue from low dose radiation exposure, on the contrary, radiation therapy, in its various forms, slightly increases, though not by much, the chance of secondary cancers down the road.
My bad. I skim read the wiki link I posted. I hadn't heard of the effect being thus termed but was very much aware of the effect.
My point about radiotherapy being the science of reducing a therapeautic dose to healthy tissue stands. That dose certainly isn't benign nor is it lethal but it can if deposited incorrectly result in secondary tumours.
Whether there are beneficial effects from continuous exposure to low doses is moot (code for contentious or you could kill your career stuff). If you want to check go to Paarl. Paarl rock is granite and granite is radioactive. AFAIR the background in Paarl is much higher than the surrounds. Personally I've seen a few mutants there