Nazila Fathi of the New York Times reports that, from 2003 until recently, Iran's Islamic government "permitted relative freedom" to the Marxist Left -- "Leftist students [who] use an anti-imperialist discourse toward the United States and say they have no plans to overthrow the Iranian government" but "refer to the government as a capitalist regime and condemn pro-democracy politicians who support change as 'bourgeois'" -- because "it rejects the liberal reform movement and attacks the West" (Nazila Fathi, "Radical Left, Iran’s Last Legal Dissidents, Until Now," 20 January 2008), though space for dissent is closing down again.
The way the New York Times reports on Marxist students in Iran (about 500, estimates the paper), they are unlikely to pose a material challenge to the government or eclipse the religious liberal opposition. They can, however, act as a protest group that puts pressures on the government from the Left on such issues as privatization (for which nearly all factions of the power elite, from Ali Khamenei down, are in favor, whether they are reformists or neo-conservatives or Rafsanjanists).
The Islamic Republic needs an opposition of the Marxist anti-imperialist sort, not the liberal pro-Western kind some of whose members are funded by the empire's "regime change" machinery, and it needs to learn to tolerate its existence again. (This is one issue on which the Cuban and Venezuelan governments, if they talk to the Iranian government about it in the right way, can help make a difference, for the Iranian government does want their support to maintain and expand its international legitimacy.) Such an opposition can only strengthen the republic.
The job of those of us who live in the West is to get the empire off the back of the Iranian people, so the dialectic of the government and its left opposition can safely and productively unfold.