Most businesses which have compensation / reimbursement tax issues, either because of heavy travel to one location or international, pay for the tax accounting services which surround these issues and "gross up" the compensation of employees adversely affected by tax consequences.

While it's expensive and time-consuming for the individual to deal with this, a good accounting firm can make short work of this. If an employee pays roughly 40% of compensation in various taxes (federal, state, social security), a $10,000 tax treatment of compensation as reimbursement can mean $4,000 for the employee. Or put another way, if the employee travels at the employer's convenience to a location for a sufficient period of time to cause his reimbursements of $10K to become taxable, most employers would up the employee's compensation by $4K+ tax on that, so that the employee isn't affected by the travel issue.