Yes, if your employer pays for employee education at all, there is no reason they shouldn't pay for an online education.
Many employers now provide programs that pay back future employees' school loans or provide funds for current employees to head back to school and earn more advanced degrees. Not all employers do this, but the ones who do often provide funds for online education as well.
If you are interested in going back to school, there are many ways to go about finding a way to get that funded by an employer. First, you can search for specific companies that offer student loan reimbursement for employment. Many companies seek out graduates who have specific qualifications, and, in order to appeal to those students, they offer them benefits including loan reimbursement. Another way to get funds for your education is to ask your current employer if they will supplement you going back to school. Many employers do this because it increases the value of their employees, and that value translates back to the company. Also, many employers can also deduct amounts spent on employee education from their taxes. If this is the case for your employer, there is no reason not to bring the matter to their attention and make them aware of your goals.
Another reason employers should have no problem subsidizing an online education is the fact that online classes are typically more flexible. Your employer will know that your pursuit of an advanced degree will affect your work performance less with distance education than traditional education. Many employees who make the decision to go back to school end up having to leave work early in order to make it to their night classes, or they become more tired and less productive during work hours. With online classes, employees are able to do everything required of them from the comfort of their own homes. Their schedules are much less interrupted, and they are able to apply what they are learning to their jobs everyday.
If you think that your employer may be interested in funding your education, take some time to explain to them why you want to receive a specific degree, how it will enhance your job performance, and why it will make you a more valuable asset to your company. Then, describe all the ways that an online education will be just as, if not more, valuable to you as a traditional education. Presented with these realities, your employer will likely at least consider your idea.