Updating to Fedora 21 broke my 3G modem connection

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Hello,

I have a ThinkPad T340 with a "0bdb:1926 Ericsson Business Mobile Networks BV" 3G integrated USB modem.

On F20, I had to set prefer_mbim=N for the cdc_ncm module for it to work, after that, it was fine.

However, since I updated to Fedora 21, creating a /etc/modprobe.d/ncm.conf file containing

options cdc_ncm prefer_mbim=N

doesn't work any more, /sys/module/cdc_ncm/parameters/prefer_mbim still contains "Y" after a reboot, which I think may be the problem in the end, even if ModemManager is supposed to support MBIM now (but it was already in F20).

Extra info: After manually setting prefer_mbim to N and reloading the cdc modules,

# mmcli -L
Found 1 modems:
    /org/freedesktop/ModemManager1/Modem/2 [Lenovo] H5321 gw

# mmcli -m 0 -e 
successfully enabled the modem

# rfkill list 1
1: tpacpi_wwan_sw: Wireless WAN
    Soft blocked: yes
    Hard blocked: no

# rfkill unblock 1

$ nmcli c up 81d31117-82cb-40d3-9f6e-a95b10975bb8
Error: Connection activation failed: Connection 'XXXX' is not available on the device ttyACM3 at this time.

I've also tried disabling the PIN, I'm running out of ideas... Can someone help?

Regards, F.