How and when you use it would depend on what you wished to achieve. It is suitable for many, many applications from systems requiring 1000’s of Amps to small power and lighting.
Ideally long straight runs are best suited to it, though not essential. You can have a large header busbar trunking (say 1000A) feeding smaller trunking (say 250A-400A), which in turn could feed still smaller trunking (say 16A)-100A).
Some busbar trunking has additional conductors that can be used to control interfaces.
There is no simple answer to this as how and what you use comes down to familiarity with the product and experience particularly on similar applications.
If you are looking for a flexible installation that changes regularly with the addition of new equipment or relocating of existing it can pay dividends both in speed and cost.
The installation itself can be much, much quicker than installing cables.
Almost anything can be done, sometimes it requires some modification to manufactures standard equipment to achieve exactly what you want, however speaking from experience i can tell you that some of Telemacinuque’s now standard equipment came from modifications requested by a colleague over 20 years ago.
Some busbar trunking is better than others, some is even IP Rate, the busbars being cast in resin.
My advice would be to take on the services of a reputable building services consultant, one of the bigger names, I currently work for WYG (Formally White Young Green), others such as Hoare Lea, BDP will be able to provide a similar level of service.
The best service will come from some one whom has actually designed schemes that use it, re inventing a wheel usually results in problems.
If you require any pointers i will gladly advise you. my mobile number is 07775783663 if you should require to speak to some one.
My colleague at WYG Manchester who is truly proficient with busbar systems is Mike Green, he is currently the technical director and can be contacted on 0161 872 3223.