Compact fluorescent lighting and single phase motors
It almost surely has nothing to do with the bulbs themselves but happens to all the devices. The bulbs are just what you see. Are you sure you don't notice it with any other devices? (fridges, microwaves, etc will most likely not show the effect because it happens too quick and not enough to turn them off).

It sounds like a common problem of simply overloading the mains. If you have too much stuff hooked up drawing too much power the mains will "sag". 

Say it's 220V but with a bunch of stuff plugged in it might be 210V. BUT when large devices like motors kick in they draw a bunch of current at the start(They surge) which drops the voltage even more. Some devices can't handle this drop in voltage well.

This can happen also on a single circuit if it is heavily overloaded but it should trip the circuit breaker OR the wire is too small of a gauge(which means you would have to add a new circuit or increase the gauge of the wire).

The only practical solutions are:


Put the lights on a different circuit. 
Increase the wire gauge on that circuit branch
Increase power supply to building. (requires Elec. Co. to do it)
Reduce the surge current to the fans(a soft start). This might be the easiest solution. Basically you buy a device that prevents the fans from coming on full speed at the start then slowly(over seconds) let them rev up. Motors generally draw the most current when they are not moving(so if they get jammed and you turn them on then they almost surely will burn up). If you don't need them to start instantaneously this seems like it would be easiest, and possibly cheapest solution. I'm not sure where to get such a device and it would depend on things like max current, max voltage, number of phases, etc... 


a quick google search gives things like

http://www.surplussales.com/Motors/starter.html

which are the type of devices you want but you need to know more specifics about your motors. (note, this will solve your problem if it is only happening at turn on of the motors. This basically makes the motors come on real slow so the lights won't notice it. It is not necessarily the best solution because it could be due to the other 3 reasons and your just patching up a pothole)

These are not mutually exclusive and it may take all 4 to solve the problem as it might be a combination.

In any case, it being a business, you should contact an electrician to keep in code and possibly not kill someone(including yourself) or be sued cause someone got a tingle up there leg.

It could always be crappy lights too but probably not.