you can stream the gps NMEA sentences through one of USB serial interfaces .We have a guide in draft.. ill get it published in the next few days.
In summary, this is what you need to do.
Connect to the second interfaces on the GSM module; minicom -b 115200 -o -D /dev/ttyACM1
Activate storing of last values of NMEA, from the GPS to the GSM module;
Activate the unsolicited aiding result. AT+UGIND=1
Set NMEA data to to stream through USB interface /dev/ttyACM3
Turn on GPS, (Start GNSS with GPS+SBAS+GLONASS systems and local aiding.); AT+UGPS=1,2,67
To view the stream minicom -b 115200 -o -D /dev/ttyACM3
To stop GPS, use AT+UGPS=0
We have some info here about the UGPS command which is used to turn on GPS.
This document describes these all these commands in detail.