This is one along the lines of 'wouldn't it be nice if'. Yes, it would be. You can get an idea of how effective this will be if you paint a good sized chunk of wall with http://glonation.com/ glow in the dark paint. The paint will likely have a much higher density than any plant based set-up will be.

This may be useful as emergency lighting in a jungle but I highly doubt that we'll be replacing LEDs, fluorescent or even incandescents with this technique.

Apologies for being terribly pessimistic but even if the project gets funded and the goal is successfully achieved I can't see the utility.

Has there been any work done on an estimate of efficiency, some sort of modelling about what reasonable expectations are with respect to output?

It's a super presentation complete with HN voting ring, congratulations on successfully gaming the system. If they are just as good at the execution then this can't fail.

edit: after reading the risks and challenges section:

"We hope to have a plant which you can visibly see in the dark (like glow in the dark paint) but don't expect to replace your light bulbs with version 1.0."

So that was pretty much spot on. Then:

"The more money we raise, the more we can refine our designs and the stronger the effect we will get so please tell all your friends about the project."

That's not very honest, there is no way there is a direct relationship between the money they raise and the effect produced, these things typically follow a saturation curve with the upper limit being pretty hard and rather low compared to other ways of generating light.