Have you tried approaching either of them? Contractors usually have a site board near entrances with the relevant site agent contact details etc, as a courtesy. Or if not the PR departments of both. They get contacted by all sorts, and I know at least a few that had photographers reach out to them. Some got invited out at key stages, some didn't. All depends on if they think the exposure and perception is worth it I guess. There was an amateur photographer on a site that ran a fairly low key blog, that ended up comissioned to do the website pictures of the finished thing out of it.