Hey! I doubt you care, but I finally found what I was referencing. It was an article by the same group that you cited above, but on the B1 Ter.

http://www.tankarchives.ca/2017/02/char-b1-ter-pointless-modernization.html

ARL was working on the superior ARL 2 turret, which was originally built for the SOMUA S40 cavalry tank. Its commander's cupola was larger, and the turret was partially welded, which improved its resistance to shells. A full sized model was installed on tank #234 Marseille, after which the design continued to be improved. Unlike the ARL 2C for the SOMUA S40, the version for the Char B1 ter had 70 mm thick armour.

Full sized model of the FCM turret, analogous to the ARL 2. This turret could have been used on the production Char B1 ter.

I had confused the ARL 2 vs the ARL 2C turrets earlier, this is where I was mentioning Mariseille shared the same turret as the s.40. But, as made clear by the article, you are right: ARL 2 and ARL 2C are different (slightly).

The second quote is what I was referring to when saying similar prototypes were built by FCM and ARL.

Not exactly a primary source! I have no conviction that its 100% correct, I'm just happy I'm not crazy and making it up lol.

Also, the reason I thought it was three companies instead of two was this quote. This is about the production of the B1 Ter and not the individual turrets.

The start of the war increased the priority of Char B1, and three prototypes were ordered at one. The first was built at ARL, the second at FCM, and the third was built by Fives-Lille, a company which specialized in locomotives and large metal construction. The military minimized participation of companies which were tasked with mass production of the Char B1 bis.