Speying females certainly does help with reducing / eliminate false pregnancies however more importantly it reduces the risk of uterine cancers.
This is an extract from the RWF information on spaying female rabbits: 'Having female rabbits (does) spayed is even more important. Most females become territorial and aggressive from sexual maturity onwards (4-6 months). They have repeated false pregnancies, and may growl at, scratch and bite their owners as well as attacking other rabbits. Keeping two females together - even if they are sisters - can make things worse. Spaying reduces and sometimes eliminates these behavioural problems.
Spayed females are likely to live longer then their unspayed sisters. Up to 80% of unspayed female rabbits develop uterine cancer by 5 years of age. Females who are not spayed when young and in good health may have to undergo the operation in later life if pyometra (uterine infection) or cancer develops, although usually it is too late and the cancer has already spread.'