There's a list of known surviving HPGs on Sarna, and counting them reveals 28 working HPGs. Most of these are in the former Republic of the Sphere; it's unknown if other states were have similar rates of survival, but if they do, there's actually quite a few HPGs in the Inner Sphere and near Periphery.
Every planet within range of a working HPG can still receive messages, but their HPGs don't transmit. Since HPGs can transmit in a 30-50 LY radius depending on the model, there's probably some HPGs that can still take to each other. I haven't bothered to try and map the known network. If you control a surviving piece of the network, then within those bubbles, you can send a message as fast as ComStar did... but information will only reach your HPGs by courier ship.
Under ideal circumstances (recharge stations at every star, a perfect line of stars spaced 30 ly apart, no need to run maintenance or load/unload cargo etc) a JumpShip can manage 90 LY every 22 days. In practice, it's going to be substantially lower, but how much lower it will be varies based on local conditions and what the JumpShip is doing. Of course, there aren't always going to be courier ships in the first place; JumpShips are still kind of scarce, and nobody can afford to dedicate many to full-time courier duty. Most of the time, messages reach you via the grapevine; news propagates along trade routes, and might not be entirely reliable by the time it reaches you.
Based on what I've seen in the sourcebooks, if you're not a high ranking military official, you get (potentially highly inaccurate) news months after the event in question has occurred. If you are a high ranking military official, you get accurate news, but it takes months for messages to get from you to your boss or from your boss to the front. For example, during the events of Tamar Rising, we see the Lyrans & Hells Horses take months to figure out that the Jade Falcons have abandoned their OZ, and additional months to find out where they went/what happened to them. So, months, not years. This of course assumes Inner Sphere conditions - if you're in the Periphery, you might not get any news for considerably longer considering JumpShip traffic is less frequent there. It also assumes there are no friendly HPGs on the path the message is travelling - they can speed it up considerably, cutting travel time down by weeks at at a time.