EC25 Notes:   
Card doesn't show up as an LTE interface in ROS 6.x unless you put it into ECM mode (NET'ed/private IP interface).

Modem needs configuring before use. Load EC25 drivers onto PC and then serial terminal to the AT commands serial port
  • In RouterOS v6.xx all of these modems will use PPP interface for communication, which means that maximum achievable connection speed for all of them is limited to around 35Mbps (limit of serial interface).
  • In RouterOS v6.39 and newer the EC25-MiniPCIe module can be configured as a LTE Interface which can support local IP address from modem. Use this AT command to enable it and after that reset the module: at+qcfg="usbnet",1
  • In RouterOS v7.xx for modems that support MBIM drivers like EC20 model, LTE interface support will be possible and it will allow to achieve full LTE connection potential.

PPP & LTE Setup Notes:

You can use "/system serial-terminal port=XXX channel=X" to enter the commands from the Quectel wiki page; if you use "/ports print" you'd get the need port#, and it should be channel=0 but you can try multiple ones. 

From the serial-terminal to the card you should be able to enter the AT commands mentioned to set the CDC mode (e.g. PPP or LTE in Mikrotik terms, or PPP or ECM in USB driver world

You may not want LTE mode as the card will act as it own router and do it's own NAT'ing on the miniPCIe, outside of the Mikrotik firewall (e.g. after the Mikrotik routing plane). 

Quectel support told a few months ago: "With ECM mode (AT + QCFG = "usbnet", 1) [e.g. LTE mode on Mikrotik], the connection will work via NAT, so the module will provide it's own local ip address to mikrotik (not the network one)".

For completeness, the USB integration modes available on the EC25 are:

AT+QCFG="usbnet",0 - is PPP & QMI (default)
AT+QCFG="usbnet",1 - is ECM.
AT+QCFG="usbnet",2 - is MBIM

While Quectel EC25 supports QMI and MBIM mode, neither are currently supported by Mikrotik. MBIM mode is what ROS v7 is promised to bring, and would make this a lot easier than AT commands. PPP mode is what I'd recommend, but you can get working in LTE mode if you use /system serial-terminal to set the needed AT+QCFG="usbnet",1 command if you want to try, and you can use AT+QCFG="usbnet",0 to get it back to working in PPP mode.

Finally, if you need to get RSRP, SINR, or RSRQ from the module, then use AT+QENG="servingcell".

Further Notes:
LTaP models when configuring the modem in PPP mode / ROS6.x you need to disconnect the terminal console from serial0 (not usb0). 

##### Modem commands quick list #####

As noted above to start comms to the modem directly connect to the serial listener

/system serial-terminal usb2 channel=2

# Set operation mode
Query current status with AT+QCFG="usbnet"

AT+QCFG="usbnet",0 - is PPP & QMI (default, documentation says Mikrotik requires PPP but have found MBIM also works)
AT+QCFG="usbnet",1 - is ECM
AT+QCFG="usbnet",2 - is MBIM (fast LTE)

# Once set reboot the modem (if it doesn't auto reboot - Mikrotik will need a power off/on)

# Quick connect to APN named 'internet' (testing only)

# Show registered network

# Show internet / ip status

# Signal Quality Report - returns received signal strength indication <rssi> and channel bit error rate <ber>

# Query network info e.g. operating band/freq

##### Mikrotik specific
# the usb serial ports can't be enumerated with directip detection on so disable this
port firmware set ignore-directip-modem=yes