You haven't given' us a lot to go on . . . Some possibilities:

Stems caught snow, so better insulated OR

More moisture since it's a bit lower OR

More shade, so more even moisture OR

Less frost heave since the snow remains there longer OR

Coincidence, since survival may be based on the particular plants there vs. other spots.

Curved border around a dying yew. Snow gets plowed into the spot. Same plants were planted all along it. Not lower. Doesn't LOOK more shaded...looks less shaded...but that WOULD explain why the snow last there longer. Less frost heave is a possibility. More Spring moisture from melting snow is another.. The spot gets less wind also, though.

More moisture was my thought too. Less frost heave makes sense too. More insulation over the winter from all that snow on top of them. I'd say, keep plowing snow there. [g]