You are right bmork! I was so deeply in that modeswitch files, that I did not even notice the syntax. Thank you very much!
The well formed and working config is the following:
{
"messages": [
"5553424308306384c000000080000671030000000000000000000000000000"
],
"devices": {
"05c6:f000": {
"*": {
"t_vendor": "05c6",
"t_product": "6000",
"msg": [0]
}
}
}
}
With this, the device switches to modem perfectly.