Watford - the maximum number of TIM shares available at conversion is 4, thus a current price of TIMPB of 90 cents implies a TIM price of 22.5 cents (90/4).
I realise this is only an approximation, TIMPP gets preference for dividends and you won't be able to convert until next september and this isn't taken into account, but I think it still a good ballpark view.
If you feel otherwise, I'd be interested to hear.