The answer to this question is simple. Everything must be in the plan. And every body corporate is bound by the Act.
For example, there is no provision for small developments of only two units to not have a plan nor is there provision for small and relatively unimportant things to be excluded from your plan. Also, even those items the body corporate doesn't pay for - such as private balconies - must be in the plan.
Just remember that your long-term maintenance plan is for the whole development, regardless of who pays for the maintenance and how big or small the job is.
You can opt out of maintaining any particular items that you choose but these items will need to be identified in the plan and the decision not to maintain must be made at an AGM or EGM.
Also, with some items, there is scope for each body corporate to decide who pays when work is carried out on them. i.e. The body corporate or the individual owner. However, these items still must be included in the plan.
Just in case you need further confirmation, “infrastructure” is defined as including such things as pipes, drains, cables, security, television reception, rubbish removal and much more.