filter width

When i interpret para 4 of ETSI TS 100 392-15 it looks like the channels are spaced at 25Khz. The default low_pass used in all of the demods is 25Khz. But when i look in the FFT of the complex signal, the 25Khz specified in the cutoff_freq of firdes.low_pass causes a passband of twice the width. Isn't this way to much? Shouldnt the cutoff_freq be 12.5Khz, giving a passband of 25Khz? (Or is there an intentional spectral overlap between adjacent channels?) If this is the cause, should we just change the parameter to filterwidth or channelspacing and use a /2 in the cutoff parm? Gr. Sim