It seems these images use systemd (a nice departure from the init.d scripts used in the previous container_vms images [1]). [1] - https://cloud.google.com/compute/docs/containers/container_v...
Yes, it runs both systemd and upstart. Staying true to chromiumos, upstart is still the /sbin/init. I believe both upstart and systemd support some subset of the sysvinit api (e.g. rc and /etc/init.d).
The previous debian based container-vm image only ran upstart.