whatcms.org can't work it out so it's most likely custom do you really need to know? you can replicate the site without using the same platform
take your pick if it's a cms it should be able to do it or you could build up from a framework or start with a blank page and write the whole thing. the key questions for me would be what are staff able to do in the backend... are they tracking the ticket from enquiry until the job is complete or is it just an online sales tool I'm a big fan of running everything from one place so I'd be looking at having everything on the site, in which case I'd probably pick a framework rather than a cms