No they have not. This is just a total misunderstanding of the technologies involved. Sadly for dumb marketing reasons 'solid state' has become the terms that is used, but that is the wrong term. The actual reason why 'solid state' was important is because people believe lithium metal anodes would only be possible with solid state. When we are talking about next generation 'solid state' we actually mean 'next generation li-ion batteries with lithium metal anode'.

The 'solid state' technology in buses that is talked about in that article is a totally different thing. That tech has been known to exist for a long time and is a totally different technology that has nothing to do with the hype around 'solid state'. Its 'lithium-polymer' that as a far narrower application and isn't all that interesting and certainly not some amazing next generation battery.

This is a sad issue in battery marketing world where people mix up what these technologies actually mean.