I think if it is maternity leave replacement they normally state that so applicants are clear on that and have no expectation of ongoing work. I work in public health and over the past few years there has been an increase of fixed term contracts. It is very difficult to get new ongoing positions created so organizations try to get small amounts of money from multiple sources and then create a fixed term position usually to get a specific project completed. I think it is always worth applying for those positions and getting a clearer picture at interview.