noone has said this is a good idea.
What would happen if a run start capacitor is installed across the 220 VAC?
IOW Can the cap be left there permanently to allow a FM intercom to
communicate across the panel?
run/start capacitors typically have motor windings connected in series
with them which limit the damage if the capacitor shorts out.
For connection across the power lines a "class X2" capacitor is
indicated.
http://www.evox-rifa.com/technote_pdf/rfi_fact.pdf
http://www.google.com/search?q=X+capacitor
Also filter X capacitors are designed to pass radio frequency, run (or start)
capacitors may not be. thus you may see adequate performance with a
much smaller capacitor that the motor caps.
larger X2 caps can be had in the form of PFC capacitors.
