I’ve been playing BP for about 2.5 months and only just now noticed that the dotted lines between buildings actually have a purpose. I had always thought them to be merely cosmetic (and noted that people frequently request that they used to “transport” in-work drugs from one building to another via port - something that I’m surprised/excited that Tim/Dev recently commented on Steam forum he may implement).
They note which plots in nearby buildings will be made available for purchase when the connected plot in a current building is purchased.
I’m sure others knew this, but it never really occurred to me - just looked for a decent shape plot w/ some ports.
(the BP wiki proved useful in this case )