I think that the modification IOSerialFamily.kext is not needed
necessary line exists in AppleWWANSupport.kext and AppleWWANSupport1.kext
but I did all the steps with the link and everything worked and stopped at that
I wrote a post to report that identical modem is working
now I have time for experiments so that everything is thoroughly tested
modem script required in my opinion, I edited CellPhoneHelper.kext for a few days without result