The 100 series does not have a pilot tone in the transmitter so this won't work because the IFB receiver requires a 30 kHz pilot tone to be present before producing audio (unsquelching). If you are trying to run 100 series transmitters on the talent, a 100 receiver feeding a recorder and then monitoring on the IFB receivers simultaneously, I'm afraid you are out of luck. 

The newer LM and UM transmitters can run in the IFB mode and the newer units will have that capability marked on the case. You could run the transmitter in IFB mode and then IFB receivers and 100 receivers would both work. However the sound quality in the 100 receivers would not very good.

The pre-emphasis of the 100 series and the IFB series is about the same. The problem comes from the fact that the 100 series has a dual band compander that treats the bass and treble part of the signal separately. If the audio signal is balanced above and below 1 kHz, the single band compandor in the IFB and the dual band compandor in the 100 will track pretty well. If the bass and treble are not about equal after pre-emphasis, then the weak band will be reduced even lower compared to the stronger band.