Under the ADA, there are some instances when the presence of a service animal can cause a fundamental alteration in the goods and services offered by a business. Having a SD in the treat
Net room with clients and there pets most likely would fall into that category. That would mean an employer could refuse the accommodation.
Animals receiving treatment, even just routine maintenance, tend to be under stress. Yes, they are a risk to other animals present, such as a SD, but the SD is also a risk to the client animal because his presence can increase that stress. I think a very large percentage of smaller animals, including cats, would be quite distressed at having a strange dog in the treatment room with them. As an owner, who shows up with up to four dogs and/or four cats, I would not allow it in my appointments. There's just no way I could supervise all those animals not used to each other while simultaneously restraining someone for some treatment. Which is another point: the SD would need supervision too, which would likely conflict with the amount of focus you need on the client animal. I just know I couldn't do it and simultaneously do an a ceptible job stewarding my dog.
You might arrange a place for the dog to be when you are actually handling other animals. It would depend on the individual office whether you could pull that off.