Our transfer switch switches both hots and the neutral.
Steve Spence
Dir., Green Trust
http://www.green-trust.org

Actually I don't think it does.

Some "alternate energy" systems are installed as separately derived sources so
they would use transfer equipment that switches the neutral. (perhaps as part
of protection for transients when the system is not connected to the building
ground)
On the other hand most "generator" transfer switches for portable generators
will not switch the neutral since the standard on portable generators is an
isolated ground. If used as a stand alone generator on a job site there is no
advantage to grounding the neutral, in fact it adds a hazard.
Fixed in place, pad mount generators can go either way. They will have a
grounding strap in the wiring compartment that you connect or disconnect,
depending on how you are installing them.
This whole deal can get pretty complicated to describe but the end objective is
to only have one point where ground and neutral is connected, no matter how the
system is switched.
When I am inspecting a complex system I have to draw it out sometimes to sort
out what is going on.