Apparently the stakes that Mattamy had in our backyard were meant to mainly help with the grading, rather than marking the lot lines. This would explain why the lot lines that my neighbour in my back measured are a little different.
Apparently the builder is not obliged to provide the buyers with stakes as to where the lot ends - normally the neighbours work this out by measuring everything together
If there is a disagreement, the town recommends purchasing the services of the professional land surveyor.