Steve McIntyre claims:

One version of the trick is used in IPCC TAR. In this version, Mann replaced post-1960 values of the Briffa reconstruction with instrumental values, then did a smooth, then truncated the Briffa reconstruction back to 1960. Post-1960 instrumental values affected the smooth by the arithmetic of the smoothing filter.

Steven Mosher claims that the same “trick” was used in IPCC AR4.

Arthur Smith investigated and shows that the 1960-truncated Briffa curve in AR4 was not padded with instrumental values, but rather with the mean of the adjacent existing values, exactly as stated in AR4.

Smith concludes:

So, conclusively, despite Mosher’s claims of certainty on what the scientists did, he was wrong.

But it sure takes a lot of effort to prove that one claim wrong, doesn’t it?