Sort of.
Here in the USA, NexTel, a popular cellular like PTT service was pretty popular for a while. Sprint (another cellular carrier) bought them many years ago and sort of killed off the NexTel brand.
Most cell carriers offer some sort of PTT over cellular service, but it doesn't seem to be as popular around here at NexTel used to be.
There are many apps for smart phones that will mimmic PTT over cellular or WiFi service.
There are even some companies that sell devices that look like a traditional 2 way radio, however work over the cellular networks.
Some higher tier two way radios are including things like WiFi and LTE. Most of that is aimed at data, but there are some that are allowing voice to transit those networks when out of range of the LMR system.
As for impact on trunked systems…
Yeah, a lot of small radio shops went broke. A lot of them were bought up by larger shops.
Two way radio service is still actively used, even leased services like smaller companies use.
I run a trunked system for work, and there were a lot of people trying to tell me the system would go unused when "everyone" switched to cell phones.
True, while cell phones are more popular and wide spread, there is still a need for radio service.
I ran a Motorola trunked system up until 2011. Had about 300 radios on that system. When I replaced it in 2011 with a NexEdge system, I kept those 300 users and over the last few years added over 100 more.
Part of the increase is because the users radios are cheaper, so that gets more radios in the hands of those that need them.
The other part is that enough major disasters have shown that the cellular networks are not robust enough to survive much. Either the systems get destroyed, or completely overloaded.
Looking that the cell sites that serve my location, how they are powered and how they are connected back to their respective networks, I'd never rely on a cell phone as my only form of communications. I've seen too much stuff to do that.