Type 15s aren't designed to take on T-90s because the T-90s are MBTs while ZTQ-15s are light tanks for mountain regions and swamps.
On the other hand, the issue is more how to conduct reconnaissance? Conventional MBTs can do recon-by-force because they're well-armored and well-protected so that if they get ambushed, the tanks are unlikely to get routed. Drone reconnaissance is good, since drones are cheap and disposable, but copter reconnaissance by Z-19s and Z-10s are going to end up meeting MANPADS and getting slaughtered. Type-15s, on the other hand, are more limited to being infantry support tanks because of their inability to knock out a T-90 in a fair fight.
Moreover, if you want to do deep penetration into Indian lines, the only tank that can actually get there would be the ZTQ-15, and when you set them up as requiring Z-10 and Z-19 support to take out T-90s, both the ZTQ-15 and helicopters are vulnerable in the assault role.
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I'm not bashing the ZTQ-15 as a bad tank, for what it provides (extreme high-altitude mobility, excellent infantry support functions), but it would be better if it had more robust anti-tank capability. As others have suggested, fire-and-forget top-attack gun-launched ATGMs would allow it to contest T-90s successfully without requiring Z-10s to do the tankbusting for it. We just have no indication that Norinco et al have developed such a missile.