'Results to be declared by the college': to be + past participal

The be+past participle construction is a passive infinitive.

The words 'results to be declared by the college' contains an example of the passive infinitive, and can be converted to the active as 'the college to declare the results'.

Note that neither of these two alternatives contains a finite verb, and so would not be considered complete sentences in traditional grammar.

Such constructions are often seen in headlines in order to save space. The to + (passive) infinitive replaces a future construction such as will or is going to.

So in this case, 'results to be declared' means 'results will be declared'. And both 'an announcement to be made' and 'an announcement will be made' are 'correct', but only the latter is a complete sentence.

There's an article about headlinese in Wikipedia, which contains the extract: "...the future is expressed by an infinitive, with to followed by a verb, as in 'Governor to sign bill'".

https://en.wikipedia.org/wiki/Headlinese