With all due respect to some others who posted, the MdTA Police does not have statewide authority - at least not in the normal course of business. This entity was created to provide police enforcement and protection for specific roads, structures, and other property under control of the Transporation Authority, Port Administration, and Aviation Administration.
The following is taken from Md. TRANSPORTATION Code Ann. § 4-208 (2014)
(1) A Maryland Transportation Authority police officer may exercise the powers described in subsection (a)(2) of this section on property owned, leased, or operated by or under the control of the Maryland Transportation Authority, Maryland Aviation Administration, and Maryland Port Administration.
Anyone can go to this section of law and read the whole thing. There are certain exceptions which would give MdTA Police authority in other areas for specific purposes and conditions, but this authority must be specifically granted by someone such as the Governor, Secretary of MSP, etc. One example of when such authority might be granted is immediately after a "9-11" type event (which I pray we never see again). Other exceptions relate to mutual aid agreements, but there are limitations. If interested, you can read a very good summary of this issue here:
http://md-lgit.civicplus.com/DocumentCenter/Home/View/1306
The bottom line is that the MdTA Police do not have statewide jurisdiction like the State Police do. However, only a fool would intentionally violate a traffic law in front of an MdTA officer outside of their perceived jurisdiction, because you have no way of knowing exactly where the boundary is or what other circumstances might give them authority at the time.