This is my opinion, but when you're on the clock you have no expectation of privacy.
When you're working, you're being paid to do a job. When you work for 8 hours, you're selling your time to an employer. Your employer has every right to monitor what you're doing with the time you've sold them.
In the call center I work in, we really don't have a "Bathroom" idle code, and its pretty redundant. Instead we have codes such as Lunch, Break, System Problem, End of Day (for doing time sheet), Unavailable, Meeting, Training, etc. We're expected to take our bathroom breaks using our allotted "Break" time (which is 30 minutes over a 8 hour day) or during our Lunch. If we have to take a bathroom break and we've used all of our break time, we can use unavailable, but its heavily discouraged.
This allows the call center to maintain their SLAs by keeping their workforce accountable for their time used, which is 100% okay.
I'm very happy with the way my workplace keeps tabs on how I use my time.