[susan53]

I'm not sure why you think it's unusual - it's a regular structure :

Main Clause
Subject: The future
Negated Verb: is not
Complement: ours (possessive pronoun)
+
Subordinate (non-finite) clause
infinitive verb : to see

As the subject of a non-finite clause is never explicitly stated, it has to be inferred from the previous clause. When a possessive is involved - whether a possessive adjective as in 1 and 3a below, a possessive noun as in (2) or a possessive pronoun as in your example and 3b the subject has to be "mentally converted" to the correct form - ours/we, David's/ David etc.


1. It's your turn to buy the drinks. (= you buy the drinks)
2. It's not David's place to criticise. (= David shouldn't criticise the plans)
3a. It isn't your house to sell ( = You can't sell the house)
3b. The house isn't yours to sell ( =You can't sell the house)