From anshi forum and Dakok, it seems any GB will work on 2030 (ICS) baseband if injected with the right libcm.so, extracted from an ics system/lib and pasted on the same in GB. Yes, at first I was skeptical, so I tested it out. First with the network working cm from anzshi (beta 1) and it worked perfectly!, and, second, with an old cwm backup I had when I'd merely my GB new phone - it works. No brick (don't believe that is possible, unless you drop a brick on it!), no fuss. It works!.
Therefore, what I suggest, after some testing, that all old GB roms, such as Grt, do this and we won't have to 'downgrade, upgrade' etc. What do you think?
NB With the old cwm backup I restored, whilst in recovery (6027), before I booted it, I used aroma fm (1.80) file browser to copy and paste the libcm.so, then booted.