Yes the two are using the exact same protocol and channels. So they can cross talk.
The S2C has a different processor on it then any other XBee module. While it has three different types of firmware to support the different protocols, you can't simply load on the Code for an S1 module on it. If you want the S2C hardware to support the Zigbee (ZB) protocol, then you need to install the S2C Zigbee function sets and code. If you want the S2C to be a Digi mesh 2.4 module, then you must load on the S2C Digi Mesh specific Code. Same with the 802.15.4 protocol, if you want it to talk to an 802.15.4 module, you must install the 802.15.4 S2C code.