Not very realistic.
HowStuffWorks has an interesting article about generating electricity from lightning. There are several problems with harnessing natural lightning:
The logistical problems involved in making it work are significant. First of all, there's the basic fact that thunder storms are sporadic and lighting strikes random; considering that energy demands are steady, dependable energy sources are preferable.
Second, it's not so easy to capture energy delivered in one enormous blast in a split second. It has to be stored and converted to an alternating current, without blowing out the collection system in a single large strike.
Third, the energy contained in a lightning bolt disperses as it travels down to Earth, so a tower would only capture a small fraction of the bolt's potential. In the end, barring the development of a technology that could capture the energy from lightning before it strikes, it's probably best to focus on other, more earthly sources of energy.
The first point should be irrelevant here because the lightning can be activated at precise intervals. The third is unimportant because there should be no dispersal (I assume that this scenario takes place on short ranges). It's the second that is an issue. Capturing 5 billion joules in one second isn't easy. Perhaps if this is on a smaller scale, it could be plausible.
With better technology (i.e. capacitors for energy storage), this could happen, but it would take a lot of improvements. In the meantime, there's a chance that you could take advantage of atmospheric effects, such as this proposal using water vapor. I don't think that the manmade bolts would have the same sort of effect, though, because the environments are different. Perhaps you could try harnessing the thermoelectric effect, or use the lightning bolt to turn water into steam, turning a turbine.
Indirect energy capture is probably the best option here.