I don't know how to write this as a batch script. If you have PHP installed in your computer it's very simple. Run php from the command line, paste the following, press Enter and Ctrl+Z (or Ctrl+D, depending on the platform).

$in = fopen ("in.txt", "r") ;
$out = fopen ("out.txt", "w") ;

while ($line = fgets ($in))
if ((substr ($line, 0, 4) == "RON-") || (substr ($line, 0, 4) == "TEC-") ||
(substr ($line, 0, 5) == "DDBT-")) fwrite ($out, PHP_EOL) ;
fwrite ($out, $line) ;

fclose ($out) ;
fclose ($in) ;

The code works if the markers appear exactly at the start of their corresponding line. Note that you may wish to change the input file name (currently in.txt) in the code.