How does city resource trading work?

I ask because I'm having issues. I tried the obvious space saving measure of having water/power/sewage on one city and zoning and developing more another city. It worked for quite a while, but now for some reason the city I play more in is lacking power. It says there are 98MW available from the neighboor city, but it's buying 88. On the producer city, I have ~300MW spare, which it recognises, also saying it's selling 88MW.

How should I go about increasing the amount transfered? Is it true that there is a 100MW cap, evenly spread between eatch city in a microregion (The ones connected to each other)? Would just waiting on each of the cities solve this? Is there any sign showing the city was synced? Is there a log somewhere? Will this work properly if playing offline?

I ask that this not be marked duplicate, I read the thread at Can't buy power from neighboring city the top voted answer just gives up while the second guy says it's all evenly spread.

Extra regional resource capacity is evenly split between connected (by road) cities.

Suppose there are 3 cities, all connected by road. 2 of them are each running a 200MW surplus, then the third city can buy 100MW from each surplus city, leaving 200 MW surplus unpurchasable.

That's the way it works.

Is there any sign showing the city was synced?

No.

Is there a log somewhere?

No.

Will this work properly if playing offline?

Yes. Make sure to play each surplus city for ~20 minutes after the surplus is obtained to be sure the server has pulled their snapshot for the region. You may also need to play the consumer city for some time before the regional snapshot is pulled locally for your use.

Here is an explanation from the devs.

Water/power/sewage is split evenly between all connected, claimed cities. From your image it looks like there's other cities connected to the producer, so the amount shared is split.

MaxisMC