This file links the text for subtitles to specific frames in a movie - specifically INTRO15FPS.mve.
The first column lists symbolic identifiers.
The second column lists a frame, at which the subtitle text will be shown.
The third column lists the string reference of the text to show.
In BG2 ToB we have:

2DA V1.0
0
           Frame      string     
1          480        70669      
BLANK      540        0          
2          1245       70670      
BLANK      1365       0          
3          1387       70671      
BLANK      1465       0          
4          1492       70672      
BLANK      1515       0          
5          1560       70673      
BLANK      1662       0