So if I'm understanding your current setup. You have your hearing aids connected to your cell phone and computer over BT. You lose the analog input, but still want to use the landline. OK, in that case the Spectrum Anywhere that LiB found in the post above mine is the path you want to follow.
You would use that app to manage your "land line" connection and make and receive calls on it.
You can visit
this site to grab the client for Mac, iPhone and so on. Once installed, you will be able to access your home phone on your computer and on the go if you wish.
Since your hearing aid is connected to these two devices through BT already, you shouldn't have to do anything else other than setup that app and learn how to use it.