stating otherwise. So, this is a judgment call.
With gas prices what they are, if you are now requiring someone who has not previously been frequenting the main office to do so on a regular basis, it seems as though the fair thing to do would be to devise some offset so that telecommuting employees are not taking what to them is essentially a pay cut. This is especially true if you want to keep these "long distance virtual employees" happy and working effectively for your company. (The company must have a good business reason for having these telecommuting employees in the first place--e.g., specific and unique skill sets and capabilities).
If you do decide to reimburse officially designated "virtual employees" for their trips to the main office, you should create and disseminate a policy to all those so affected and communicate it to potential new telecommuting employees, too. You might want to specify that mileage over 40 miles each way will be reimbursed for employees officially designated as "virtual employees" who use their personal vehicles when
they are required by management to be at the main office. Or you may want to say that the company will reimburse all mileage for employees officially designated as "virtual employees" when they are required by management to be at the main office. It's up to you.
You can look up the government mileage reimbursement rate by going online. Input "CONUS rates" to your search engine and it will take you to www.gsa.gov. Then click on "Policy." Here's a quote from that site: "On June 23, 2008, the Internal Revenue Service announced an increase in the mileage reimbursement rate for privately owned automobiles to 58.5 cents per mile."