Can I see all bookings in Google Calendar?
Yes, with the links in Setup → Google Calendar.
In Setup → Google Calendar there is a link for Every clean (for the office) and one for Each cleaner's own cleans. Press Copy, then in Google Calendar choose Other calendars → From URL and paste it.
It is read-only: change bookings in Spick HQ, not in Google. Google refreshes these calendars every few hours, which we cannot speed up.