As there is no direct evidence to explain how it would affect them I would assume,
With the Knight of One, Bismark, I would dare say he wouldn't see the "before images" thus unable to predict their movement. Considering that he was the Knight of One and had his eye sewn shut, I would assume it wouldn't hinder him all that much not having his Geass as he would have been able to prove himself to others without his Geass (he position of Knight of One may have been just because he's in league with the Order)
With Marian, I dare say it would kill her has it was her Geass which kept her alive in Anya. If she was in her own body she wouldn't be able to transfer her conscientiousness so had the Canceller been in use when V.V attacked her she would have died
With Mao it would be similar to how his Geass Power reacts with those with The Code. Effectiveness depends as Mao became focused on C.C so much because she was the only person he couldn't read the mind of, on the one hand The Order could use it to prevent their secrets being discovered but on the other hand Mao may affiliate himself as a member of the Order because he would be with other people he can't read the minds of, a sense of peace for him
The problem is that the Geass the Canceller dispelled in the series were Geass Powers which didn't benefit the caster directly. with Marian's, Bismark's and Mao's Geass there are sustained effects and they reap all the benefits (ie. Marian can jump bodies, Bismark can just react with foreknowledge and Mao can gain info from other's minds) as such the question needs to be asked how the Canceller would work with them. Would the Area of Effect shown when Jeremiah used it (the blue sphere) apply an "immunity" effect to those in the area or would it only work on who has it equipped.
the one point in the series were we could see wether or not the Canceler applied an immunity effect is when Shirley dies. Lelouch is using his Geass on her but we don't know if it was having any effect on her has his order was to keep her alive when she had been shot and on the verge of death. also if she had immunity to Geass it may have been as a result of her dying, as shown when Euphie was dying and the Geass effects on her was dispelling.
Given that Bismark is in league with The Order there is the chance functionality against his Geass may have been developed as the Canceller worked on the Geass Effects of current members and one person who was their captive (and the children who forced a Knightmare Pilot to shoot his allies during the attack on the Order may have been a by-product of research on Lelouch's Geass given it's similarities).