Hi RedCactus
If you have a look at the 2 announcements on 02 April you will see that Morgan Stanley announced that they had bought a net approx. 7 million shares, taking their holding to 61.5 million shares (from 54.5 million shares). The Mitsubishi Financial Group announcement mirrors the Morgan Stanley announcement since these two parties are related and Morgan Stanley is holding the shares on behalf of Mitsubishi.
Regarding shorting of a particular share, to do this you need to have shares to supply. So for example, if I thought Westpac shares were totally overvalued, I may decide to short them. To do this I would need to borrow some Westpac shares from someone who owned them (I'd pay them a small fee for renting their shares) and I'd sell the shares (and deliver them to the buyer in 2 days as I'm obliged to do). Then, when the Westpac share price went down, I'd buy the shares back, give them back to the party that lent me the shares and make a good profit (my sale price less the cost of buying the shares back less rent paid on the shares).
Having said all this, you would not buy shares just to lend them out. Those that lend them out are natural holders of the shares eg. they hold them as part of following an index etc - it makes sense for them to lend them out as they are holding them anyway so they may as well earn some rent on the shares in the meantime. Shorting can be very lucrative for finance co's when they get it right but of course it is also risky - if the share price gaps higher you can suffer big losses. Also, it is only available to institutions and sophisticated investors.
(20min delay)