/lib/udev/rules.d/70-printers.rules is in system-config-printer-udev 1.5.7+20160212-0ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | # Low-level USB device add trigger
ACTION=="add", SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", ENV{ID_USB_INTERFACES}=="*:0701??:*", TAG+="udev-configure-printer", TAG+="systemd", PROGRAM="/bin/systemd-escape --template=udev-configure-printer@.service %p", ENV{SYSTEMD_WANTS}+="%c"
# Low-level USB device remove trigger
ACTION=="remove", SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", ENV{ID_USB_INTERFACES}=="*:0701*:*", RUN+="udev-configure-printer remove %p"
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