Clostridium tetani (C. tetani) is a bacterium commonly found in soil and is excreted in the faeces of many animals (both mammals and birds) and serves, by means of the exotoxin, tetanospasmin, causes the life-threatening condition tetanus.
Soon after asking this question I found a reliable source, the National Institutes of Health. It can survive for over 40 years.
Clostridia form endospores and can survive for years as a dormant spore. You can check this article about viability of clostridial endospores but it doesn't really talk about how long it can survive.
$\begingroup$ The paper however includes a general passage on endospores saying that: Once they are formed, endospores can stay dormant for extended periods of time, from thousands (8, 13, 20, 25, 33) to millions (3, 35) of years, although for the more extreme claims of longevity it is difficult to rule out modern contamination (37). So apparently the potentially survial is extremely long. $\endgroup$ Sep 5, 2013 at 9:23
$\begingroup$ yeah.. i did read that statement but thought that it is too hyperbolic :P $\endgroup$– WYSIWYGSep 5, 2013 at 10:56