Yes, just as you can do with the Encore Partyline, you can connect studio IFB to the HelixNet. It requires the use of the PIC-4744 and the MA-704 for control. The following drawing represents the signal flow for this to work.
MS-702 or another Clear-Com Partyline Power Supply is required to power the PIC-4744
HMS-4X will not momentarily mute active talks to the partylines during an IFB call initiated from MA-704. It will however turn on the mic on the HMS-4X whenever a button is pressed on the MA-704.