The strike price as you refer to it is the price at which the principal amount of the bonds gets converted to shares.
In this case the bond holders would consider converting their debt to shares at a price higher than the real share price because the other option is to bankrupt the company by forcing them to default when the company can not pay cash to redeem the bonds at their maturity dates (in which case bond holders may get nothing, so perhaps it's better having a few shares).
