the argument that wearing a crucifix equates to wearing a scarf for a Muslim woman is utterly erronious.
For Muslims, their faith is bound up in the daily lives in a way which Christian faith is not - a scarf is an obligatory part of daily dress for a Muslim woman, a cricifix is not, it is merely a symbol, but not required display by the Christian church.
Again, wedding rings are customary, but not compulsary, and if my employer found an H & S issue that made wearing one a risk, I would take mine off in works time.
If the hospital chooses to exercise its health and safety policy, then as an employer, it is entitled so to do. Regulations change constantly in all public services, and the length of time when a regulation has not been in place, or enforced, is really not relavent in this argument.
I believe this lady is making an unecessary issue here. Of course her faith is important to her - but is it vital that she advertises her faith to everyone in this way? I sugggest that she may wish to demonstrate her faith with a religious symbol, but if that conflicts with her employers' rules, then she sould remove it during working hours.
I think she is on very dodgy legal ground trying to take legal action over a symbol which is just that - a symbol, and which has no neceseity in legal terms to be worn and displayed as part of her duties in the hospital.