Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
It is permissible to pray behind any Muslim regardless of his juristic affiliation.
Answering your question, Dar Al-Ifta Al-Misriyyah, states:
The issue of refusing to pray behind a fellow Muslim due to differences in jurisprudence or due to following different schools of law is a reprehensible matter which Muslims ought to refrain from.
It is historically noted that renowned scholars following different schools of jurisprudence did not show a shred of discrimination against those who followed a different school of law.
It is reported that Imam Al-Shafi`i did not perform qunut in morning prayer when he was praying in Iraq near the graveyard of Imam Abu Hanifah although it is a confirmed sunnah in his school of jurisprudence. When he asked about it, he said, “How can I refrain from following him during his presence?”
Eminent Muslim scholars from among the Prophet’s companions did not cause enmity nor sow discord among them due to their juristic differences. The essential value of keeping unity and not to be divided by our differences is a vital message of Islam.
Prophet Muhammad (peace and blessings be upon him) said, “Do not have estranged relations with one another. Do not nurse enmity and do not have envy against one another. O worshippers of God! Be brothers!” It was also narrated by Abu Hurairah that Prophet Muhammad (peace and blessings be upon him) said, “The obligatory prayer is essential behind every Muslim, pious or impious, even if he has committed sins.”
Based on the above, it is permissible to pray behind any Muslim regardless of his juristic affiliation.
Almighty Allah knows best.
Source: http://www.dar-alifta.org/Foreign/ViewFatwa.aspx?ID=10501