do they have pricing based on utilization?
I've been told it has rarely been used but HP has a model where you get X amount of storage and you pay for what is written, which sounds like a good model for service providers. You can leverage wide striping of say the 3PAR platform (or VMAX if EMC has a similar pricing model available) for good performance from day 1 and are able to spread the costs out as you add in customers. vs a more traditional approach where you may not be able to afford to buy one of those $1M arrays up front and instead start out really small - and the I/O penalty you pay for being small and have a more difficult time building up.
Per the HP program I don't know the details around it, there may be minimum level commitments over time and stuff. The program might of even have existed in 3PAR prior to being bought by HP I don't know, I first heard about it last fall.
3PAR of course has had self provisioning via the Virtual domain software package for years now (up to 1,024 management domains in an array) - though I don't believe there is any specific integration with fancy APIs or metering stuff specific to service providers.