MML Being Relisted In GDXJ, page-4

Yes I think it is bullish but you probably have to get in before others get a sniff that it will be added to the index. A lot of people are aware of the index effects now. Analysts publish specific notes with predictions about additions/deletions.

Van Eck typically seem to buy about 4-8% of some of these companies but precise number depends on weighting in the index etc. Van Eck hold 7.85% of BDR for example.

The volatility/liquidity in these rebalances is often described using 'Average Daily Volume' (ADV). MML trades ~1m shares per day then it would be about 16x ADV (at 8%). That's quite high.