It is likely not emulated. You can see the second screen reacts to whats going on in the main game. While its technically possible with emulation to achieve this effect (as far as I've seen from screens) it would be awkward and require many work arounds. All in all, I wouldn't bet on emulation being the case.
However, an emulated game could possibly be within reason, technically. Remember that while emulators on the DS now, through means of homebrew, are far less efficient than if it was an officially made emulator.
Case in point, the PSP can emulate PS1 games without skipping a beat. There is a vast difference between officially built emulators as opposed to fan ones. The main difference is, the official emulators are build with full knowledge and documentation available, along with official bios and other utilities freely available to the developers. There is no guess work, or reverse engineering, which leads to a much faster and more accurate emulator.