Like all photography questions the answer begins with "It Depends".
You will hear that T-Max (and some other B+W films) are capable of resolving 200 lp/mm on the negative. However, what you rarely hear is that is only at a contrast ratio of 1000:1. This means using a special test target of black and white lines where the contrast ratio between the black and white lines is 1000:1 which is 10 stops. Very Very Very rarely if ever in the real world would you ever find a subject which has that contrast ratio in the finest detail of your subject so you can forget any notions of achieving 200 lp/mm in the negative. The more realistic lower contrast ratio in the fine detail of your subject is 1.6:1 and when the contrast ratio drops to that you will only get 63 lp/mm on the negative (for Tmax 100 quoted by kodak).
So in reality the achievable lp/mm on film is limited by the subject finest detail contrast ratios which will be somewhere between the the upper and lower limits of what the film is capable of. And there's the crux of it. Your subject will have varying contrast ratios throughout it. Some parts will be fairly high and some parts very low so the resolution throughout your negative will vary greatly. If you can achieve 100 lp/mm on film you will be doing extremely well but that will only be areas fine detail with strong subject lighting providing high contrast. Other areas not in direct lighting will have very low contrast and low resolution.
Most modern lenses can easily resolve the subject detail that is available to them from the subject contrast ratios.
So I would assume that average lp/mm you can expect in your negative is say 60 lp/mm and that will allow you a 6X enalrgement factor which has some margin of error thrown in.
However, it isn't as simple as that becasue it doesn't take into consideration the human eyes ability to resolve detail (the so called 8 lp/mm) at 10 inch distance. The print sniffers of this world will cry foul when they put thier greasy little noses up against your print but ignore the fact that when you stand back and look at a print from a sensible viewing distance related to the prints size, you don't need anywhere near 8 lp/mm in the print for it to look sharp and highly detailed.
It's the combined print resolution and viewing distance that determine what will look good. So once again there is no fixed answer becasue it depends on all these factors. But your 60 lp/mm on film will be good enough for bigger than 6X enlargements if they are not viewed from 10 inches away but several feet away.
There is a formula somewhere posted on the web for calculating required print resolution for viewing distance.
Note1: F22 which is the default goto aperture on a 150mm lens on 4x5 LF is diffraction limited(Rayleigh Criterion) to 70 lp/mm so you could never achive more than that at F22.
Note2:
A 150mm enlarging lens at F11 producing a 12X enlargment would be using an effective aperture of F143 capable of producing 13 lp/mm in the print. But starting from 60 lp/mm in the neg you would only have 5 lp/mm from the original subject. Your enlarging lens is not the limiting factor except that they are optimised for certain enlargement factors, 150 lenses around 6X with a few exceptions designed for bigger enlargements such as Rodagon G lenses. But they can't get higher resolution than exists in the negative so really for a 4x5 neg you are looking at 12X before the image really starts to break down and that is only providing you have excellent taking lens, excellent subject fine detail contrast ratios, excellent dof in subject, excellent technique, perfectly aligned enlarger, excellent enlarging lens etc etc etc otherwise all bets are off. Hence my 6X suggestion and Dans 8X suggestion which are ball park about as good as it gets depending on your lp/mm in final print criteria.
