I think so. Can't speak for Tanzania, but in Kenya, almost everyone I speak to would say nasoma is "I read" & ninasoma is "I am reading". Happens in most cases e.g. nijua = I know, tuende = let's go/we should go. Anyone else want to chip in..? I'm no expert.
in tanzania it's common to shorten any first person present tense verb to cut out the ni- prefix. "nasoma" would be common here too as you said it is in kenya.
While I haven't heard people say "nijua", I have heard "najua" to mean "ninajua."
"tuende" or "twende" is a separate thing though. this is a polite command (as evidenced by the "e" at the end, rather than an "a" as in "kwenda), not an abbreviated present tense verb.