That's not entirely true.....the new tractors and trailers do have liens on them, but the first part of the loan was unsecured (the portion that paid health and welfare)..... this is what I have read when it all went down, I will try to find a link....so the government will get in line with all other unsecured creditors...
Update, I couldn't find anything that explicitly said it was unsecured but I did find this that leads me to believe it is....why would you receive stock for a secured loan?
"The company used the loan to meet payroll, health care, pension costs and capital investments. Yellow said the loan helped keep employees on the payroll. The company employed about 30,000 employees at the time, 24,000 of whom belonged to the Teamsters union.
In return for the loan, the Treasury received nearly 16 million shares of Yellow common stock, making it the company’s largest shareholder with nearly 30% of its outstanding shares."