/lib/udev/usb_modeswitch is in usb-modeswitch 2.1.1+repack0-1ubuntu1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | #!/bin/sh
# part of usb_modeswitch 2.1.1
device_in()
{
	if [ ! -e /var/lib/usb_modeswitch/$1 ]; then
		return 0
	fi
	while read line
	do
		if [ $(expr "$line" : "$2:$3") != 0 ]; then
			return 1
		fi
	done </var/lib/usb_modeswitch/$1
	if [ $(expr "$line" : "$2:$3") != 0 ]; then
		return 1
	fi
	return 0
}
if [ $(expr "$1" : "--.*") ]; then
	p_id=$4
	if [ -z $p_id ]; then
		prod=$5
		if [ -z $prod ]; then
			prod=$3
		fi
		prod=${prod%/*}
		v_id=0x${prod%/*}
		p_id=0x${prod#*/}
		if [ "$v_id" = "0x" ]; then
			v_id="0"
			p_id="0"
		fi
		v_id="$(printf %04x $(($v_id)))"
		p_id="$(printf %04x $(($p_id)))"
	else
		v_id=$3
	fi
fi
PATH=/sbin:/usr/sbin:$PATH
case "$1" in
	--driver-bind)
		(
		dir=$(ls -d /sys$2/ttyUSB* 2>/dev/null)
		sleep 1
		if [ ! -z "$dir" ]; then
			exit 0
		fi
		set +e
		device_in "bind_list" $v_id $p_id
		if [ "$?" = "1" ]; then
			id_attr="/sys/bus/usb-serial/drivers/option1/new_id"
			if [ ! -e "$id_attr" ]; then
				modprobe option 2>/dev/null || true
			fi
			if [ -e "$id_attr" ]; then
				echo "$v_id $p_id ff" > $id_attr
			else
				modprobe -r usbserial 2>/dev/null
				modprobe usbserial "vendor=0x$v_id" "product=0x$p_id" 2>/dev/null
			fi
		fi
		) &
		exit 0
		;;
	--symlink-name)
		device_in "link_list" $v_id $p_id
		if [ "$?" = "1" ]; then
			. /lib/udev/hotplug.functions
			wait_for_file /usr/sbin/usb_modeswitch_dispatcher
			exec usb_modeswitch_dispatcher $1 $2 >>/dev/null 2>&1
		fi
		exit 0
		;;
esac
exec 1<&- 2<&- 5<&- 7<&-
(
		. /lib/udev/hotplug.functions
		wait_for_file /usr/sbin/usb_modeswitch_dispatcher
		if [ -x /sbin/initctl ] && /sbin/initctl version 2>/dev/null | /bin/grep -q upstart; then # Test if upstart is running
			exec /sbin/initctl emit --no-wait usb-modeswitch-upstart UMS_PARAM=$1
		elif [ -d "/run/systemd/system/" ]; then # Test if systemd is running
			exec /bin/systemctl --no-block start usb_modeswitch@$1.service
		else
			exec /usr/sbin/usb_modeswitch_dispatcher --switch-mode $1 >>/dev/null 2>&1 &
		fi
		exit 0
) &
exit 0
 |