Employment verification

I was out the night before and I was drinking. I went to work the following evening and I was called off of my route for a Radom dot drug and alcohol screening. The test came back positive for alcohol only. The levels where not high enough to charge me with a d.u.I. However they did discharge me for the small amount found in my urine because of the policy I was discharged from my position. I applied for another driving position with a different company and when they requested my verification of employment with the previous company they told them I was discharged for a positive dot, the company is exempt from dot policies they don't require your dot because it isn't needed to drive for that company and therefore a release of such information is not within the company policies. However the companies that I wish to apply for does require a dot back ground check. I don't have anything negative on my actual dot back ground. Can this company give out any medical back information without my consent as a verification of employment to the companies that I have recently applied too?