Expenses really should come with receipts and a prior agreement to pay them. An unofficial treasurer paying himself expenses can’t be done without some sort of agreement from the Owners Corp.
An owners corp can agree at an AGM to pay ex gratia payments to EC members retrospectively for work done the previous year. That’s it.
To answer your question, is it legal – the answer is probably not. You could let the new guys sort it out but this will be outside the scope of their normal duties and I wonder how much they’re going to charge.
Is $600 expenses for 13 years of voluntary work really that much? Some accountants charge $50 an hour, rather than a year.
Frankly, bearing in mind that your relationship with your one and only neighbour is in serious strife, I’d be tempted to say that you are prepared to let this go as a gesture of conciliation – it’s a small price to pay to begin repairing your relationships.