Note that I do NOT know much about email servers and that is precisely the point. I eat iptables rules for breakfast, I can set up a Debian server from scratch and I can certainly configure a mail server. But there's more to it than meets the eye. Been there, done that. And we got burn.
I don't know "why", but all I know is that we had problems!
tl;dr: 30 team person startup and we tried to use our own mail server. Too many problems. We moved to Google Apps for domain and all our problems were fixed...
As for using a previous owned spammer domain, I strongly question that logic. Black lists tend to be both conservative and done by copy-pasting. A blocked domain abcd will not block abc or abcde. If the block lits do not see mails from abcd within a month or so, they also tend to remove them to clear up space. This time frame is also way below common domain name expire dates.
Regarding reverse lookup, I assume that 30 team startup bought a company network contract from the ISP. Such deals should include support and static IP, which mean reverse lookup is a single email away from being done. Co-location contract might be different, but I wouldn't know.