Hi Ruslan, this is a special shorthand only used for newspaper headlines to make them more succinct. Newspaper headlines also often omit articles (the, an, a) for the same reason.
to + verb in these cases can definitely be referred to as the "to infinitive" form of the verb, but the function is not the same as the normal function of the "to infinitive". So it's best to think of this as a special journalistic shorthand.
As Calvin said, it refers to the future, i.e. "be going to" or "will". So the full longhand sentence would be:
[A/The] city will recruit neighborhood trash collectors to improve [the] [waste disposal] system.
Because this is a long sentence, it doesn't attract the reader's attention quickly. So the newspaper editor removed the parts in square brackets [ ] to make it more succinct.