From typicallyspanish.com

Madrid
900,000 affected by bus strike in Madrid today
By h.b.
Apr 7, 2008 - 7:53 AM

Metro services are being strengthened in Madrid today as the capital suffers a second day of strike action on the buses. 900,000 travellers are expected to be affected by the EMT stoppages programmed between 0530 and 0800 and between 1630 and 1900.

Minimum services have been established at between 50% and 60% depending on whether there is a metro alternative route.
The stoppage is over pay and working conditions and more stoppages are planned for Wednesday and Friday this week, and on every weekday next week.