I found a way that seems to be keeping the cell information after reflashing the FW, here are the steps.
In normal case, these are the steps used to flash the firmware:
flashtoolcli1.exe --cfgfile flash_download.ini --port="COM7" probe
flashtoolcli1.exe --skipconnect 1 --cfgfile flash_download.ini --port="COM7" flasherase 0x350000 0x54000
flashtoolcli1.exe --skipconnect 1 --cfgfile flash_download.ini --port="COM7" flasherase 0X3BB000 0x1000
flashtoolcli1.exe --skipconnect 1 --cfgfile flash_download.ini --port="COM7" burn
This will cause the module to erase (I suppose) the network information, and consequently, the module will take time to re-obtain such information after the startup (in my tests, around 3 minutes).
So, to avoid this 3 minutes wait, I am doing only the step 1 and 4 of the above commands, without requesting to erase:
flashtoolcli1.exe --cfgfile flash_download.ini --port="COM7" probe
flashtoolcli1.exe --skipconnect 1 --cfgfile flash_download.ini --port="COM7" burn
And, the module after restart gets the IP address imediatelly. So, no need anymore to wait for the 3 minutes.