1

Isn't the first of november an official holiday in France? All Saints.

2

I used SNCF French site, and found:

Leaving Nice ville 7:55 via Marseille arriving 11:29 Aix-en-Provence Cenre
Leaving Nice ville 7:31 direct arriving 10:45 Aix-en-Provence Centre
calls the Aix-en-Provence TGV station 10:12 to 10:25

That's all that's running that day.

There's one leaving on 31 October Nice ville 18:55 via Marseille arriving Aix centre 23:55...
but unless you have someone meeting you there, I don't think it would work well.

This is the site I used:
http://www.voyages-sncf.com/billet-train

hope this helps...
and yes, Liberat is correct it is All Saints (Toussaints):

"Public life in France is generally very quiet on All Saints’ Day. Post offices, banks, stores and other businesses are closed. Outside of tourist areas, restaurants and cafes may also be closed for one or more days. However, some stores in Paris, as well as at airports and railway stations and along major highways, are open.

Public transport service schedules vary depending on where one lives and intends to travel. Churches may be closed for visitors who do not wish to take part in the services and guided tours may not be available".

3

Nice ville 7:31 direct arriving 10:45 Aix-en-Provence Centre - as said in #2 would be the best. This is a TER (regional) train and you dont need any reservation for.

4

Is there any chance to get to Aix by bus? Their schedules say nothing actually. We fly in to Nice around 3 pm and would be great to leave for Aix later the same day. Regarding trains I understand: a day off. But the Nov. 2nd looks equally disappointing...

5

By coach have a look here: http://www.phoceens-cars.com/transport-paca-ligne-ler-nice-aix-en-provence-marseille-horaire-et-tarifs-c1-p3.html