That won't work because it would take a monster of a ups to run those lights for more than a couple minutes.
If you loose power you loose power... Not much you can do about it other than add some daylight. If you always have lights on with normal day cycle you could install one of those skylight tube thingies. (I have no idea what they are called right now, but someone will know the name of it.)
But you'd have to have a cover on it so it's not a beacon of light all the time from your grow lights and also when the days are too long you'd have to manually cover it.
No it would not be enough light to grow, only enough light to keep them on schedule.
No real reason to worry about it either way unless you are growing a strain prone to hermie if the lights are messed up.
