I've been a little slow on hacking lately, but here are some notes.
In Truce Dome, 7F01F4 bit 1 is set. This is mirrored to 7E1BAB for overworld access.
If that bit is set, overworld events check it at [0034], and go to [00A3]. That's an AddObject for [119E]. [119E] has AddObjects for [1576], [1585], [15A4], [1594], [159C], and [15AD].
You'll need to copy [00A3] and [00A7] and [119E] to [15B3] into the apocalypse events, which can go at the end. If you select [119E], you can shift+click on [15B3] to select everything in between.
Once everything is pasted in, select [00A3] on the apocalypse events, and press label to change the label. It doesn't matter what you name it.
Starting at [000F], there's a series of similar commands, If(Mem.7E1BAx & yy) Goto [zzzz]. Add a new command with the command button in that area (it doesn't matter exactly where), select category Comparison, command Comparison, Addr Type Mem, Value 7E1BAB, Addr 1, Operation &, and for Label the very last item on the list will be your custom label. Press Update, then Write Mem.
This should get the events working. If there are any issues, let me know.
I *was* going to just leave some notes for now, but I guess they turned into instructions. Oh well.