Thanks, gentlemen.
If it's a new Boeing procedure, perhaps reports of this nature will become more common (and highlight the fact that there may be icing above 10C).
Re TAT probe icing. Unfortunately, as far as I know, there is no way of comparing the Left TAT probe temperature with the Right TAT probe temperature. The Left seems to be used for displays on the Upper EICAS and on both CDU's. It seems that only a Left TAT probe heat failure or a Left ADC failure will force the displays to use the Right TAT probe.