Wireguard is easy to block. Some VPN providers do implement an obfuscation layer for it, but Tailscale uses plain WG, so if WG is blocked, you will get no connection. Control plane would still work, though.
I haven't actually tried this when my home service is down, because it's basically never down, but I can easily switch exit nodes when they are both running without hitting the authentication servers again.
I can understand the work network policy, someone could use Tailscale to leak data, but a residential ISP should not block it. I would rather bother their support for an incomplete service.