Add elements to collection conditionally
You could do a loop over the elements that you are always adding:

for (var info in ["basket", "account", "delivery", "payment", "placeorder"] {
    this.state_collection.add (new OrderWizardState ({ state: info, phase: this.phase_collection.findWhere ({ phase: info }) }));
}


And to add the special one, you use your if statement and insert it at a specific index:

if ( _.has (this.regions, "lp")) { 
    var state = new OrderWizardState({ state: 'loyaltypoints', phase: this.phase_collection.findWhere({ phase: 'account' }) })
    this.state_collection.insert (2, state);
}