Now you have transicc (former icctrans) and therefore you can check one of the new features of lcms2. That's what is called "unbounded CMM mode"
What is that? Well, with lcms2 you can use floating point values. That means, you are no longer limited to 0..255 on 8 bits or 0...65535 on 16 bits, but on some profiles you can get out of those bounds and the CMM still works.
Not all profiles does accept that. You need profiles that are implemented using enterly math expressions. Some very simple profiles works in such way, for example AdobeRGB. The sRGB profile does not work because it has curves implemented as tables, but the built-in sRGB does work as instead of tables it uses parametric curves. Also some advanced profiles for digital cameras using multiprocessing elements may work in unbounded mode. Right now it is hard to find any of those, as they are described in an addendum to the ICC spec.
Let's check this feature. Using AdobeRGB to the built-in Lab in transicc:
C:\lcms-2.0\bin>transicc -i AdobeRGB1998.icc -o *Lab
LittleCMS ColorSpace conversion calculator - 4.0 [LittleCMS 2.00]
Enter values, 'q' to quit
L*=0.7287 a*=0.0000 b*=-0.0000
Nothing special, but let's try this one
L*=114.6770 a*=0.0006 b*=-0.0005
Do you see where I'm going? 300 is above 8 bits, and L*=114.6 is a highlight, so here you have an example of what can be accomplised with this mode.