Yes it can be calibrated using the proper hardware. I have a retina display macbook and also a Spyder Elite 3, and I can calibrate it to match my 23" desktop monitor.

The result is pretty close, side-by-side, the colours are almost identical.

Inaccurate default settings of the Macbook

This is true. You were also right about the high contrast. I was stupid enough to carry out some adjustments on about 200 photos on my macbook before I ran the calibration. Most photos turned out to be quite washed out (to a point where it looks fake and horribly photoshopped) on my calibrated 23" desktop monitor.

By default, it renders black much darker than what it should be, so I had to lighten it up using the "Shadow" slider in Lightroom 4.

In terms of colours, it is pretty accurate by default. However with the unreasonably high contrast, I feel that properly calibrating it is an absolute must if you intend to do any photographic work on it.

Since I have invested in a Spyder, I stopped trying free/software solutions. I have searched for free alternatives, however I snatched a Spyder when it was on sale and discovered that the best free/software calibrating tool is nowhere near remotely accurate.

Easily one of the best piece of tool that gives me identically accurate colour rendition across multiple computers laptops and monitors. It is not even that expensive just around $100.