I did an analysis of their music from Mediabase, and they work with a library of 50 currents, 115 recurrents, and 168 gold. Looking at the gold, only about a dozen from the 90s, with Garth, Shania, and Tim McGraw being the artists. The oldest song is Garth's Friends In Low Places, and it gets two spins a week. They're also playing Garth's new song in their currents group, getting 22 spins. Looking at the Top 50, it doesn't actually mirror the Billboard chart, because they're trying to work in a handful of new artists, building familiarity among the bigger stars who get the most airplay. Country is all about building new acts, and typically about a dozen break through with their first hits every year.
As I said, this is similar to a CHR presentation. The station is very heavily weighted to currents, with the Top 3 songs getting over 65 spins a week. That's 9 times a day, or every 2 hours. Then there's a handful getting 50 spins, another handful getting 45 spins, and so on. The record labels have access to this information, and can monitor what songs the station is playing, and how often.