An IBEC, such as the Tech-aero will limit the current that a shorted out ignition module can draw. While a shorted ignition module is rare, I would not directly hook an ignition module to the receiver bus or "Y" it to the same battery as the receiver without the current limiting and noise filtering that the IBEC provides.
If an ignition module does short out, you'll know it within 1 second, since that's about the time it'll take your engines sudden case of the quiets to reach your position on the flight line, you're not going to be flying around too long with that shorted out ignition.
Pete