If a collective agreement allows for additional premiums for work on public holidays, this additional premium regularly only has to be paid if those public holidays are statutory.
In this case (See Resources below), the claimant was working shifts for an employer in Saxony-Anhalt. With regard to the employment relationship the collective agreement "Versorgungsbetriebe“ (TV-V) is applicable. In accordance with sec. 10 par. 1 lit. D TV-V the employer is entitled to an additional premium of 135% per working hour for work on public holidays. On regular Sundays the collective agreement allows for a premium for work on Sundays of 25% per working hour.
The claimant put forward that he is entitled to a premium of 135% per working hour on Easter Sunday and Whit Sunday.
The Federal Employment Court however ruled that the claimant is not entitled to such a premium since federal state law of Saxony-Anhalt rules that Easter Sunday and Whit Sunday are not statutory public holidays, but regular Sundays.
Bundesarbeitsgericht, Urteil vom 17. August 2011 - 10 AZR 347/10