(09 Aug 2015, 3:17 pm)S813 FVK wrote I thought they did too. Never actually paid much attention but then i cast my mind back to when the coaches were on the X9 and B7s on the X10 and just had this random thought that if they didnt interwork then, would they now (obviously couldnt interwork then as neither livery had branding for both services on (although the X9 livery did state that it worked with the X10 providing a 30 minute frequency)) and it turns out, if my '10 minute layover at each end' theory is correct, they dont.
I think when the Volvo B7TLs were on the X9/X10 there may have been some swapping buses around over the day, all I remember is the 1100 X10 Newcastle - Middlesbrough and return journey used to be operated by a Volvo Olympian. Think it was something to do with fuel.