Some things said in the comments are wrong and misleading.
Reason why the printer ask for lineart at 1200dpi (AND bitmap mode) is because it has almost the same quality as a vector once printed. It needs to be in bitmap 1bit. If your printer asks for it, he's totally right.
If you manage the black text the same way as the CMY, you'll end up with "hairy letters" if it was scanned text. That's why it needs to be at very high resolution and in bitmap (tif, eps); your print-ready file should also keep that resolution.
Maybe the lpi is consistent across all plates but there is truly the "wrong" and the "best" way to handle your text scans before getting the files to the printer. It makes a difference as much as using vector text versus rasterized text or CMYK vs RGB! These are details hard to know for someone who has never work in prepress and cheap printers won't argue with you if you want to have your texts at 300dpi and looking fuzzy!
Black is the color that can hide the most bad surprises in printing, it must be verified in a different way than CMY. There's the rich vs pure black issue, there's the text quality, the overprint itself, black that is not truly 100%, black 100% on a composite and not enriched, etc.
Be careful with the 300lpi "press"; a lot of them are in fact digital press that imitate the offset effect. They cannot be used for big projects. Real offset wide format presses are worth millions of dollars; for example, a "small" Mitsubishi 6 colors 200lpi 60" can cost up to 2 millions dollars and requires a special installation (building) because of the vibration,its size and weight. Not many printers can afford this. A digital press is worth about $40,000-$300,000. When printers advertise for 300lpi, go visit the print shop. Most of the time they do not print in-house or they use a digital press. Keywords that give hints about digital: eco-friendly (unless it's soy inks)
What's wrong with digital printing? Inconsistency. Too many factors can affect the quality (eg. needs to be warmed up or the colors will be too red, has a very poor alignment in duplex, doesn't keep its color from start to end of the run, etc.) I really don't suggest using digital printing for any prestigious project unless it's for something small like wedding invitations.
In any ways, if a printer says he can do 300lpi (realistically 175-200lpi), then you need to provide 600dpi files to make sure you got the top quality, and 1200dpi for scanned texts (in bitmap 1bit). But if you can scan arts or images or texts at 2400dpi, do it; on drum scan if possible and if you can scan the negative, that's even better. Don't bother scanning at home if you want top quality; ask your printer.