No, it's not a study saying that there is evidence of iron deficiences. If you read the BMJ article (there's a link on one of the other threads), it's just saying "hhm, this is interesting, should we look into this a bit more. We should do some more studies." about all sorts of aspects of the six month recommendation. It's an opinion piece.
It's typical knee jerk hysteria by the media on any topic involving breast feeding becuase it, shock horror, involves breasts for something other than fun. Perhaps a bit hardline of me, but I think the reporting is pretty misogynistic.
For me, it just reinforces the importance of looking for (genuine) signs of readiness for solids.
Agree with ribenaberry, the BMJ article says there is some evidence of lower iron levels in EBF to 6 months infants, but they don't say whether that is "lower but still within the healthy range" or "lower and a cause for concern".
Also we don't know whether this affects all EBF to 6 months infants equally, or more effect for prem babies, babies whose mothers had low iron during preganancy, etc etc etc.
The guidelines haven't changed, this is just calling for more work.
Article also points out that EBF to 6 months is so rare that it is difficult to collect data on this group