First, you need to keep in mind that it is the company's responsibility to make sure that I-9s are properly completed and maintained including that documents presented to complete the form are inspected. So if it hires someone at remote locations, it should make sure the job is done right.
The USCIS web site has the following information:
REMOTE HIRESIt is not unusual for a U.S. employer to hire a new employee who doesn’t physically come to that employer’s offices to complete paperwork. In such cases, employers may designate agents to carry out their I-9 responsibilities. Agents may include notaries public, accountant, attorneys, personnel officers, foremen, etc. An employer should choose an agent cautiously, since it will be held responsible for the actions of that agent. Note: Employers should not carry out I-9 responsibilities by means of documents faxed by a new employee or through identifying numbers appearing on acceptable documents. The employer must review original documents. Likewise, Forms I-9 should not be mailed to a new employee to complete Section 2 himself or herself.