The short answer is, the infinitive verb form can express the future. I'm sure you've already seen this usage in "headline" English? :)

A. ABC technology began construction on its three new factories[ to be ]built over the next eight years. To be built is the passive infinitive of the verb build, the infinitive to build B. ABC technology began construction on its three new factories which will be built over the next eight years. Will be built us the future passive of build Sentences A and B mean the same thing. C. The first of the factories [ to be ] built is company's largest factory D. The first of the factories which will be built is company's largest factory Sentences C and D follow the same logic as A and B

Hi -- "To be built" or "to be xxxx" is a passive construction. 'Built' is the past participle and in this case, the example implies that it MAY be built, but it's not definite. It's 'scheduled' to be built, or it's 'supposed to be built'. A future tense construction would be more definite. "The factory WILL be built." Generally, if you use future, there'd be a subject performing the action. "ABC company will build' (active) or "The first factory will be built by ABC company." (passive). This kind of construction can be very confusing, even for native speakers. In your second sentence, 'to be built' is also clarifying that you're talking about the factories already mentioned. Of the three factories to be built (that we just mentioned), the first one will be the largest.'