MultiMediaCard API, realy?

They can be part of the Symbian DevKit (which you can license/get if you're Symbian Platinum partner).

Actual device manufacturers may include them in their SDKs, but they don't have to (so, if whatever manufacturer/device you're targeting have not left it/them in their SDK, then you won't get them from that manufacturer either).

In other words, each Symbian OS licensee can leave out or change things that they get from Symbian (and they can also add things that Symbian didn't have).

So, the first thing is to check the manufacturer's public SDKs:
http://forum.nokia.com/
http://www.sonyericsson.com/developer
http://www.motocoder.com/

Some background data & thinking:

The only devices with Symbian OS 7.0 are UIQ 2.0 and UIQ 2.1 devices from Sony Ericsson & Motorola (maybe BenQ, too, but they're not really selling their Symbian devices, or if they are, they're hiding it well).

Nokia has used 6.0, 6.1, 7.0s (note the 's'😉 and 8.0a in Nokia's Symbian based devices. 7.0s is binary compatible with 6.1, but 7.0 isn't.

I haven't paid attention - or checked - which OS version these APIs appeared (i.e., whether they're only in 7.0. but not 7.0s, for example).