Regrettable news
It has been 6 months since the treatment. Regrettably it doesn't seem that Alastair has made any improvements, or, if he has, they are very minor. We have seen more drastic changes by changing the dosage of his medicine (baclofen and artane), though even these are fairly slight.
It is my suspicion that the nature of Alastair's injury (bilirubin damage to the basal ganglia) is somehow unable to benefit the same way that other forms of cerebral palsy can. Maybe because that region of the brain is too isolated, or because of how it was damaged. The only things I can think of to try are to use neural progenitor stem cells or to inject the stem cells into his globus pallidus directly with stereotactic surgery (or both), but as far as I know this isn't something being done for minors.
We talked to Dr. Steven Shapiro (the kernicterus expert) and he suggested that when Alastair turns seven he might be able to have stem cells injected at the same time as having DBS electrodes placed, though I believe that's contingent on some studies being done between now and then.
At any rate I can't say I regret having tried, since I know I would have always wondered. As far as I know, bone marrow stem cell treatments had not been previously tried on children with kernicterus, so now there is at least some public record of things that do not work so that we can move forward with other treatments.