The Studio Polygon buses by the looks of it have separate announcement files and slightly different file location so it might work if you copy any announcement files you have into it.
Normal buses use this with then a folder of the map name.
Studio Polygon buses use this and then a folder of the map name.
My best shot at an answer, not my area of expertise.
Go to this thread and ask, they'll know more:
Fellowsfilm submitted a new download: TSLP: The South London Project (2015) - Not Addon London! The original South London Project, out of date but uploaded by popular demand This content created by @Rhys is hosted by Fellowsfilm as abandonware. Not Addon London! This project is now hosted...
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