My intention here is not to write a full review of this DLC, but just to make a few comments about it.
1) It bears repeating that the new Seddin package, made by Aerosoft, includes the entire Berlin-Leipzig route. The yard facilities at Seddin are extensive and offer a lot of opportunities for shunting-based scenarios, even none of this type is included in the package. However, all switches within this complex are automatic, which, sadly, makes using the functional turntable impossible.
2) The package also includes a DB232 diesel engine made exclusively for this DLC by virtualRailroads and closely resembling the products in their Expert-Line series. The separate manual provided for this engine includes at least one important error: the keyboard control for the handbrake (visible behind the 2nd chair in the cab and also operable with the left mouse button) is <#>. Of course, that symbol is produced by pressing <Shift>+<3>, which has no effect on the engine. As we all know, pressing <3> activates the external-rear camera in TS. I opened a ticket at Dovetail Games Support, to which they replied by repeating what the manual says, adding that, "there is no Camera 3 in this DLC": both statements are false, leading me to wonder whether DTG ever tested this engine.
The messages regarding this engine's operation that pop up in the upper-right corner are exclusively in German and therefore unintelligible to anyone who does not understand that language. This becomes useless and frustrating to those of us who lack German at the start of each scenario: when a scenario opens, the engine appears ready to run, but a second or two later the emergency brake activates and the engine shuts down, leaving the desk and cab lights as the only operable controls. Any attempt to adjust the reverser, brakes, or throttle produces a pop-up message in G-e-r-m-a-n
. Even those of us accustomed to reading the manual before driving probably will not remember the required start-up sequence or, if they do, will then be frustrated by trying to use the <#> key to take off the handbrake. 
Just for the record, another version of this engine, made by Aerosoft, labeled "DB BR232", and lacking advanced controls, is also available as DLC.
3) Mighty Seddin Freight comes with the same old set of freight cars included with nearly all of DTG's German routes, as well as some very familiar passenger equipment. Surprisingly, the 6 included career (
) scenarios are all freight based, although they do include passenger trains among their abundant AI rosters. Curiously, all AI trains are named "opposite train" followed by a number or a pair of letters 
) Unfortunately, not one of them involves any shunting activity beyond coupling to an already assembled train -- usually after driving an implausible distance to reach said train. As a certain ubiquitous tweeter would write, "Sad!" 4) Once again, do not be fooled by DTG's misleading statements: Mighty Seddin Freight is a standalone package that includes the entire Berlin-Leipzig route.
. Great write up and very informative. 
) I had made a simple experimental Standard scenario to test the MSF turntable. After deleting B-L, I opened that scenario for editing and discovered that the area of the yard in which the TT stands was visually barren of most tracks as well as terrain features. The tracks are actually present, appear in the 2D map, and can be driven on, but the sight is peculiar to say the least. I have now restored B-L to my Steam collection and all is well visually again.