It is being incorrectly detected as a USB mass storage device, there also appears to be a problem reading the productID string.
The device node
/dev/usb0 is not an indication of proper detection, that is probably used by libusb applications to access the USB bus.
This may or may not have been fixed in NetBSD's source tree yet, you can obtain developmental releases from the following site:
http://nyftp.netbsd.org/pub/NetBSD-daily/
If it is not, you may wish to submit a bug report.. or send a message to their mailing lists.
You may also want to consider trying OpenBSD, support for cellular modems is quite mature.
Good luck.