fund change notice

is a fund change notice to participants required when the share class is being changed due to action by the fund board of directors. expenses will be lower.  

Without evaluating which rules and other legal considerations a fiduciary might consider, wouldn't one want to tell the good news?

Or is this about evaluating plan-administration expenses?

I doubt that there is going to be a blackout so a SOX notice would not be needed.  However, a new 404a-5 notice should be issued with the new fund information, with a cover letter explaining that the fund company has closed xyz fund and the money will be automatically transfered to the abc fund, etc.