You can get the information from calling any lab but they will be more forthcoming in talking to a client.
In the private sector, absent a CBA, you do not need to give notice of a drug test. In fact, you can require that they report to the test center within a certain time frame of notification. You can even drive them there. Scoop them up at the beginning of a shift. Just make sure the test is being administered in a state that the company understands well. If the driver is in a distant state on a run, you may want to seek legal counsel local to the state in which the driver is located at the time you require the test. If meth can be caught on a hair sample, and I don't recall if it can, then the time since last use is largely irrelevent