I recommend checking out the below links.
Hopefully these will tell you what you need to know.
Link 1:Shows a categorical view of current planned strikes in Italy in the local public transport sector
You will need to translate the page, if you are in Google Chrome, you will be automatically prompted to do so. If not, go to google translate website and paste in the url of link 1.
If you are looking for a particular date when there may be strikes, your best bet would be to go to the below address.
Search for Italian Strikes
Here, you are able to search based on details you enter including date, location, sector etc. All fields are optional. Again, translate the page first. The sector you are likely interest in is "trasporto ferroviario" for trains and "Trasporto Pubblico Locale" for local public transport. In the list of strikes, clicking the symbol on the right will give you more details on the strike, especially the intended duration.
If you do not know any of the date, location or sector, link 1 will show you strikes in columns - the date, the location, the sector, details and location.
Link 2: Italian Strike Information from Italia Rail
In short, Itallians plan their strikes in advance. Details of when strikes are scheduled can be found on link 1. If there is a specific service you are wanting to check, please comment it below.
In response to your bonus question,
"If your train is providing local transport during essential services for the peak times (from 06:00 to 09:00 and from 18:00 to 21:00 Mon-Sat) these will be are guaranteed. Some long-distance trains are also guaranteed on all days including holidays."
"Essential services mean that you will be transported to your destination somehow asap, just not nessecarily on the same train as originally booked."