Can Digi's XBee ZB modules communicate with other manufacturer's Zigbee modules?

Yes. The XBee 3 Zigbee RF Modules provide wireless connectivity to end-point devices in Zigbee mesh networks. Using the Zigbee 3.0 feature set, these devices are inter-operable with other Zigbee devices, including devices from other vendors. With the XBee 3 Zigbee RF Module, users can have their Zigbee network up-and-running in a matter of minutes without configuration or additional development.

In order for the ZigBee devices from two different manufacturers to communicate with each other, it's required that they both are operating on a similar ZigBee Stack Profile.

By default, Digi's XBee ZB modules operates on Digi's proprietary manufacturer's profile. This is ZigBee Stack Profile that impliments some additional features of the mesh networking. Therefore, the modules would not be able to communicate as expected with another manufacturer's ZigBee device. Changing the ZigBee Stack Profile on these modules is quite convenient with the software selectable "ZS" parameter. Using the AT commands below and with help of X-CTU software, one can change this parameter to appropriate value. See the table below in order to select the appropriate value for your ZigBee network:

"ZS" parameters 1 and 2 represent standard ZigBee stack profiles as described by the ZigBee Alliance. If a 3rd party ZigBee device supports any of the public ZigBee Stack Profiles, then your XBee module can be configured to communicate with it using the commands described above.

See the XBee 3 Zigbee 3.0 Module User Guide for more details.