Correct me if I'm wrong, the entry level Omegas are still using ETA calibres. However Omega's Steven Urqhuart has declared that they will incorporate CoAxials into every single model subsequently. The difficulty they face is to do so for the smaller sized calibers such as those for ladies models.
Some higher end Omega chrono models in the past used FP1185 architecture based calibers and Lemania 1861/1866/1873/321 instead of the Vj7750.
Subsequently Omega introduced the Co-Axials into the ETA & FP based calibers such as the 3313 which was a FP1185 architecture based chrono. The non CoAxial version was the 3303/3301.
The 2500 is basically a ETA 2892-A2 with a CoAxial escapement.
All the CoAxials are limited for Omega use only within the Swatch Group.
Starting with the Hour Vision project, the 8500 and 9300 calibres were developed from the ground up incorporating the CoAxial from the onset and not based a modification of existing calibers. This are definitely inhouse and also considered 3rd generation CoAxials.
Some horologists argue that the FP architecture based CoAxials were already inhouse movements as it was built by Omega using the basic base plate architecture but with major component changes to improve amplitude, inertia, revolving mass, etc.