Can an NRI file an RTI from abroad? What about OCI card holders?

Yes for NRIs: the RTI Act gives the right to "citizens", and an NRI remains an Indian citizen, so they can file - the Central portal (rtionline.gov.in) works from abroad, and postal filing works with an Indian correspondence address for the reply. OCI and other foreign nationals are generally NOT covered, since they are not citizens. Practical tips for NRIs: use the online portals where available, give an email along with the postal address, and for state matters check whether that state's portal allows filing without an in-person step - our state-by-state portal guides cover this.