Virginmedia moved their email hosting to Google in 2010. Only had to move it back because Google decided to stop doing ISP email any more. (Or at least that is the story I heard)
I have all ten of my VirginMedia (ntlworld) ISP email accounts in use. Used on forums like this when I don't need to be tracked back to my own personal or business domains. Or online sites I know will send spam. Or plain don't trust.
This makes spotting scam emails trivially simple. In my case there are two huge magnets for spam. My ebay\paypal address (probably sold on from EBay sellers, or hacked out of their infected PCs, or plain lifted from the insecure Ebay\Paypal sites). My other spam magnet is the email address on my website - that one is on lots of spammers spam lists.
Where I don't get any problems is with my own NTL addresses. The only problem ntlworld address I have is one that used to be owned by someone else which I picked up in 2008. That gets some weird spam. Spam that is very common to ntlworld users. I can often contact a small handful of my clients and "compare spam" and find that we have been sent the same spam from the same spammer in the same run. But this only ever happened to that one reassigned address. Never happens to the original accounts I setup in 2003.
If this hack works on the basis of an address book on the webmail site, then this explains why I have never been hit. BUT if, as is claimed, the scam also trawls the emails in the inbox for addresses then I would have expected to hear something.
As some above said - 70 reports out of the millions of VM customers does point towards a very small but weird issue.
Could be worse... just look at TalkTalk!