Pat is correct that some plants (e.g. tomato) are damaged by continuous light. However, some people keep their daylily seedlings under 24 hour lighting and don't report any problems. As far as flowering initiation is concerned, daylilies are considered day-neutral and therefore not affected by daylength aka photoperiod. Daylilies are popular in commercial landscaping such as around parking lots and other areas with night street lighting and that doesn't seem to bother them.
As far as other plants are concerned, yes some are affected by street lighting but it depends on the plant and the type of lighting. It's more likely to affect photoperiod responses, which primarily react to red light (such as from an incandescent bulb or high pressure sodium). The light intensity to affect photoperiod response doesn't have to be anywhere near as high as for photosynthesis, in fact it can be quite low, as little as 10 foot candles.
Edited to add BTW the wavelength range for PAR (photosynthetically active radiation) is around 400 to 700 nanometers).
