(Some of) the threads:
"Merge two day pages"
https://mail.gna.org/public/planner-el-discuss/2006-11/msg00045.html
"multiple locations?"
https://mail.gna.org/public/planner-el-discuss/2006-12/msg00009.html

The general problem of synchronization of planner pages is difficult, but in restricted cases it can be solved.

1. A particular case ("strong synchronization") is having the exact same files in 2 locations. Then external tools and techniques can be used since the problem is not planner-specific:

. synchronization (rsync, unison, usb-key...)
. revision control systems (centralized, distributed...)

In both cases (synchronization & RCS), care should be exercized so as to avoid the manual merging problem.
A possible solution is to use cron-like tools to synchronize/commit automatically and regularly.
Another possibility is to use "hooks" to planner functions to perform synchronization or commit

2. In the general case ("loose synchronisation"):
. (at least) 2 locations, home & work (maybe also travel)
. some pages should be synchronized/merged (e.g. the plan page related to planner itself),
. some pages should not be synchronized/merged (e.g. work related restricted pages which should not appear at home)

specificities of planner should be taken into account (timelog, planner-id, links, day pages vs. plan pages, tasks vs. notes...).

For example, tasks-ids for the same task can differ between two locations.
Multiple-plan-pages tasks and notes (tasks and notes appearing in several pages) probably add difficulty to the problem.