public transport around the south of France in February/March?

As far as I know, there's no change in the schedules. It may not be high season in the south of france, but you'll find there are still plenty of tourists from other countries to get away from the cold (at least that's what I'm telling myself). Maybe ask the place your staying at for their input? The train doesn't go to St. Tropez, I think. If you can't find anyone else who answers, PM me. I'll ask someone on my end.

Lignes d'Azur runs most if not all of the buses from Nice to surrounding towns.

https://www.lignesdazur.com/en

My trip was in May, so I don't know anything about winter schedules. My guess is that you will be fine. The tourist office in the detached building in front of the Nice Ville Station was extremely helpful to me in 2017. It should be able to answer just about any question you can come up with. It had a stock of brochures covering a bunch of neighboring towns.

The only case of summer-only bus service I'm aware of is the bus to Les Baux de Provence.
Otherwise, close to the large metropolitan areas of Marseille and Nice, winter should not affect much.

As far as I know, there's no change in the schedules. It may not be
high season in the south of france, but you'll find there are still
plenty of tourists from other countries to get away from the cold (at
least that's what I'm telling myself).

Not to mention all the people that actually live there and still want to get around. This is not some tiny greek island where everything dies down after tourist season, Provence-Alpes-Côte d'Azur has a population of over 5 million.

The train doesn't go to St. Tropez, I think.

It doesn't, but there are buses to Saint-Tropez.

The only time I go to the Côte d'Azur and Monaco is during the winter and I use both the Lignes d'Azur buses around Nice and the Monaco buses (a different system but comprehensive in Monaco) as well as the trains and trams.

I have never waited very long for buses and the schedule is quite dense. Never noticed any problems with it not being summer.

Public transport is orientated towards residents, not tourists. That's the reason for the not infrequent complaints that you can't get from one out of the way tourist attraction directly to another out of the way tourist attraction.

As people rely on public transport for getting to work/school/shops and is subsidised from taxes it only makes sense that the services are orientated towards residents and operate on a year round basis.

I am the OP (I think that's the correct abbreviation) but somehow have ended up with two different forum accounts. Just wanted to thank everyone for the information - I will book flights tomorrow and look forward to exploring on transit