Not strange. In fact quite logical.
When the notes convert in 2011, AZZ will either give you your $2 back or give you shares (esp if share price was greater than $2).
Therefore, if you bought your own shares back at 40 cents, then held them as treasury stock for a few years, then dished them out again when the price is past $2 to eliminate a conversion of conv notes, then that is a 5fold gain for the sh'ers.
Stops current dilution of ords.