Why not post the official screenshot from the HL2 Update blog post (HL2 recently had Bicubic filtering added)
https://cdn.fastly.steamstatic.com/half-life.com/images/halflife220/lightmap-filtering.pngAnyway, as for my 2 cents, AFAIK the shadows and lights in SS2 are essentially pre-baked, and were done at a reasonable resolution to begin with as a result (since there's no performance hit for pre-rendered shadows of any quality). Since entities don't really cast shadows (at least, not more than ultra basic ones), bicubic filtering would likely not do very much.