One think to consider is that during the first two years of Airbus or Boeing ownership, the aircraft will be modified to their standards.
Which “standards” you mean???
Software, paper, and some structural to meet their concepts of planning. Components to improve maintenance.
For example, the E2 has predictive maintenance. It would be inefficient to maintain a separate code base from the A320. So the best of the E2 will remain and go into the A320 also. The rest will maintain E2 specific constants and subroutines, but the A320 code will take over.
Maintenance plans will be aligned to the owning company standards to cut costs. Some details of the subsystems will have to be modified as they weren't built to the buying company's maintenance standards.
Initially, it will be a minimum, but not zero. Repairs will be analyzed to Airbus/Boeing standards. All re-engineered components will go through buying company engineering reviews and will be held to their internal processes. By this I mean structural design, testing requirements, electrical grounding, details on coatings, coatings, surface preparation, all the way to align with vendor specifications and manufacturing processes.
Booth the E2 and A220 need PiPs. All the PiPs will align to the buying company's standards. We live in the process generation and aerospace is process driven.
Airbus will force vendors to align to Airbus process on electrical noise, control logic review, use their wonderful mathematical proofs on control logic, fatigue. For stress calculations, align with Airbus vibration, stress limits for each materials, shock assumptions, and acoustic assumptions.
Boeing will do the same for the E2. Both will force vendor alignment to reduce costs on as much as possible as quickly as economical.
Both the E2 and A220 are certified for 60,000 FC and 90,000 FH. To extent those, which I believe is required, the buying company will insist on their structural standards to simplify review. Right now we see about 26 year old A320s being retired at about 26 years or about 4,600 hours per year. Unless A220s/E2s will be scrapped at 20 years, they must have a PiP.
Flight control and maintenance software will be assimilated. So will maintenance plans.
IM messages to mods on warnings and bans will be ignored and nasty ones will result in a ban.