In North America, the Sports Video Group (SVG) does an annual survey of a bunch of the major companies that rent out OB trucks:
https://www.sportsvideo.org/2017/02/21/ ... le-online/As of 2017, 3.6% of the trucks in operation were SD only, although I have a feeling the remaining SD trucks probably don't get much use and are soon to be decommissioned. In the 2011 survey, 20% of the trucks were still SD.
If you're curious, there's a lot of other interesting info in the survey as well such as the brand of cameras, switchers, etc. that are in use in the trucks. This is mostly targeting the higher end of the market, so it may not include all of the smaller trucks and vans out there, but is still an interesting snapshot.