By the wording of this LITRG News item, they're hopeful the initiative will come to something. I can't find the word 'taskforce' in the Joint Statement.
The statistics show that in recent months there has been a significant improvement in overall post handling times, but HMRC recognised that this improvement is not consistently reflected in the actual experience of taxpayers and agents. It was agreed that the whole area of post handling and processing should be looked at in depth to understand how far the recent improvements are reflected in the actual experience of taxpayers and agents and why the experience and perception of HMRCs customers is sometimes different from that of HMRC managers.