Hello!
Yes, it's possible, you shoud set up scheduler to do it.
For monday playlist, add new task, set "monday" in the days of week section ("use date" option should be unchecked), adn in the "filename or command" enter "load c:\monday-0400am.pls" (without quotes, and change the path from c:\ to where you have playlists).
Also, I'm not sure what .PLS playlist format is, and I don't know if Radioboss be able to read this format.
