This lily is odd because of its hosta-like evergreen leaves. It is tolerant of shallow planting, weekly mowing, poor soils, and dense shade. The flower is like an Easter lily. What is the variety name?
Given that it grows on poor soils, is shallowly planted, is evergreen (since it stays green this time of year), and has a white easter lily like bloom. I would guess it is Madonna Lily (Lilium candidum) (USDA zone 4-5).
Photo of Lilium candidum at VanDusen Botanical Garden, taken July 2005 by Stan Shebs.
A photo of madonna lily's evergreen basal growth, resembling your photo, can be found at Dave's Garden.
If the plant in question is growing in USDA zone 8-9, there may other options.