Segment Rates For EOY Valuations

[Guest merlin]

How are the transition rates to be calculated for EOY vals? For a 12/31/08 val, date, for example, our sofware provider blends the December 08 segment rates with the January 08 CB rate. Their rationale for using the 1/1 CB rate is that the CB rate is based on 412(B)(5)(ii)(II) which references the "...beginning of the plan year".

The IRS Notices all refer to the "...rates... applicable for (month)", so their position seems to be that the segment rates should be blended with the CB rate for the same month.