I've come across installs from competitors that have used bungee cords to do this.  It's usually a problem if the wiring comes in near the bottom of the rack and bunches up behind things.  It you can get the wiring up higher in the wall and also in the back of the rack you'll end up with a nice slack loop between the two that will let you slide out the rack and then push it back without anything bunching up. 

The best analogy I can come up with is how the hose works at a gas pump.