I have never seen any Automatic Transfer type MCCB before, but it would be a good idea!
Have seen Manual Transferring Devices - Three Pole Double Throw Manual Switches.
One of the most difficult obstacles you will be confronted with is how to route and tap the Generator Output Feeders in the existing Switchboard Sections.
The 400 Amp Section would likely be the easiest to deal with - as it would be a "Stand-Alone" item, tapped off of the Line Side Bus Kit.
Place a 400 Amp 4 pole ATS at the 400 Amp Service, route the Load Side Feeders from the 400 Amp Main OCPD to the ATS, then Terminate the Panelboard feeders to the ATS Output.
The SDS Generator's Feeder would be Tapped for each Transfer Switch, with an OCPD included with each Tapped Feeder.
The 100 Amp Meter Sections will be more of a challenge.
If you are able to obtain a direct replacement Transfer Circuit Breaker, with an equal Frame Dimensional size - AND offers Over Current Protection for both inputs (Utility + Generator), then the Generator Feeder could be Tapped with multiple 100 Amp Feeders, Terminated directly to the Tenant Meter Main Transfer devices.
Otherwise, you will need to perform the same installation per each 100 Amp Service Section, as was described for the 400 Amp Service:
- One (1) 100 Amp 4 Pole ATS per Tenant Service Section,
- Intercept existing Panelboard Feeder at Main Breaker's Load Side - run to Output Side of corresponding ATS,
- Install 100 Amp Feeder from Main Breaker Load Side to corresponding ATS "UTILITY" Input,
- Install 100 Amp Feeder from Tapped Generator Feeder's OCPD Load Side, to corresponding ATS "GENERATOR" Input.
Each 100 Amp ATS would have a Feeder terminated to the "GENERATOR" Input, which is Tapped off the Generator's Output Feeder. These Tapped Feeders would have an OCPD placed at the Tap point.
This is just a quick assumption, so please explore other options.