As far as I am aware L'oreal do not own Gatineau. Gatineau formulations stay with Gatineau and they don't make for anyone else, sell on their formulations, or make a weaker formulation or make products under another name for any other brand. The only collaboration/partnership I know of that Gatineau had was when Revlon helped out Gatineau financially, but Revlon still have no ownership over Gatineau it was just a money lending/loan agreement. Revlon also helped out with the Defi - Lift foundation providing Gatineau with the make-up/cosmetic ingreidients, which was one of the first partnerships around then, now you have Olay doing something similar with Max-Factor and people predict that you will start to see a lot more partnerships, or inter-brand collaborations in the future.
http://en.wikipedia.org/wiki/L'Oréal
The above link is for L'oreal and gives you at the bottom of the page who L'oreal own the infomation is as reliable as it's going to get concidering it's Wikipedia.
As for the layering, professionaly speaking (I am a male beauty therapist ), I would put your serum on first, then your oil then your cream. The confusing part is that many brands do steps in a different order, like Decleor you would use your oil first then prolagene then your day/night cream, you can also layer prolagene under any of the Decleor balms but let the prolagene sink in first or it will roll off, but Liz Earle use the cream first followed by the oil because Liz's oil is much richer. With Gatineau if anyone has the serums from Gatineau, you would use them first because some of them have a xanthum gum base which would roll off if you put a Decelor oil on first, not a good look I can tell you, from personal useage you end up using more product. Hope that helps.
P.S. Sorry for the long reply for my first post
