Can only comment on the early style cab 11/12 setups.
I have seen two types of cutout for the canvas " speaking tube "
On my first C8, on the cab roof panel, there is a right angled triangle shaped frame for the canvas tube to the wireless body . I still have this cab roof, can take pics if you wish .
The other type is a rectangle shaped cut out used on the C8/F8 FFW vehicles with the 1A1 body . I have drawing for this .On the FFW vehicles the cab rear glass was replaced with a metal panel, the rectangular cut out for the speaking tube has those canvas fittings .
The cutout style on your pic is new to me , never seen it before
After the WS19 set became available you would think the speaking tube would be obsolete because the WS 19 has the crew intercom facility
