Inmyopinion, the calculation of the 10 year plan is an inexact science
Having disassembled a few professionally prepared plans , it surprises me of the simplicity of their method.
I believe they just use a spreadsheet
Getting a list of capital items is simple especially if you already have starting point.
Make a guess when they need to be replaced. Make a guess as to the replacement cost
Make guess for inflation
The 10 year CW plan is more for guidance than exactitude
As time passes you will find you have too much or too little money in the account. Make adjustments yearly to the levies.