You will have to modify the source code of the RW/CSV. I dont remember which one is the MT8 exactly so this is how you would do it in general.
Sound files for announcements and that sort of stuff go in BVE's Sound folder. Create a folder and place all your recordings in wav format for the route you wish to add announcements too. Make note of the filenames.
For Example C:/Program Files/BVE/Sounds/TransitA
TransitA is my folder where I will be placing all my wav files.
Sound1.wav is a recording that I made and will put in the game, this file goes in the TransitA folder.
After you've put all the sound files in the folder, its time to open up the route file. You can usually find it in C:/Program Files/BVE/Routes/ and you should see rw or csv files. Open the file of the route you want to modify. You will need to make use of notepad's Find tool to find certain strings.
For RW files search for @station. You will see something like this, @station(95th Street,10.2530,10.2600,1,ats,\R\95dep.wav)
As you can see at the very end of this, you see \R\95dep.wav This is the location to where my sound file is. All you have to do is modify or add this value if its blank (since the MT8 route has none, its probably blank) to the location of where the sound file is.
You should also make sure that it is typed after a specific amount of commas otherwise you could be modifying the wrong value. It should be after the 5th comma, if it doesn't have it, keep adding commas until there is a
5th comma.
For CSV files its a similar search. You search for .sta in CSV files, and add/modify after the
10th semi-colon. For example on the L,
.sta Rockaway Parkway;8.5330;8.5400;0;1;0;0;;20;45;\l\canarsiel.wav,
If the sound doesn't play, you may want to check to make sure the filenames match with the locations you put it in. Or you can try to convert the wav files so that they are BVE 2/4 complaint here, by downloading the sound conversion utility
http://www.bvestation.com/devservices.php but this shouldn't be nessecary.
I hope this helps, if you have anymore questions, feel free to ask.