My guess would be no but you will have to read the details of the router and mifi device to be sure.
The MIFI device is a router so it may not even have the feature to run as a modem.
The largest issue is that even if it can run as a modem it would be designed to hook to a PC not a router. The mobile broadband routers need to contain drivers for that device and its not like you can load them like you can a PC. It will pretty much depend if the router manufacture felt it was worth the effort to integrate the driver.