Bob:
You can make a Y connection between the IBEC and a regulator. The Rx Power lead from the regulator to the receiver does not do anything actively with the signal wire (JR Orange, Futaba White, Hitec Yellow, Airtronics Blue). It's there to provide a path for radios that have DSC (Direct Servo Control) capability, or to allow the use of a bind plug and/or data monitor in the charging jack if it's a Spektrum type setup. So it's just a wiring pass through from the receiver's channel to the Charging / DSC / Bind / Data Monitor port. Thus, when you Y it with the IBEC, the signal is available for the IBEC to look at for ignition power On/Off control, same as it would be if you Y'ed it to a servo.

You could really pick any servo-type connection to Y a regulator to, it's just that things like DSC or binding will obviously only work if the regulator Rx Power lead is connected to the appropriate channel (Normally a designated battery plug location on the receiver).