Citi mortgage will subordinate up to a maximum combined LTV of 100%. Above that # is case by case but the usual answer is no. The conventional mortgage guideline for max CLTV is 95% so you should be fine.
For anyone else who may have the same question, here is what I know about other lenders:
Wachovia: They will not subordinate anything at this time regardless. This may change in the near future as they integrate with Wells Fargo.
Bank of America: They will subordinate to a new first mortgage but the first mortgage cannot exceed the existing principal balance. All closing costs and pre-paid items must be paid out of pocket by the borrower. (this is one of the most ridiculous policies I've heard of)
Wells Fargo: Great to deal with but it will take 4-6 weeks to process. Rule of thumb is 100% CLTV but will exceed that # with no ceiling if the subordination makes good sense. You will have to document and present your case to get the exception.
General rule for HELOCs: Most HELOCs can be subordinated to a new first. However, it is likely that the line limit will be reduced to 80% of the appraised value (90% on a case by case). If the current line balance exceeds 80% then the line will be reduced to the current amount owed. Subsequent principal payments could cause further reduction of the line limit.
National City: General rule is 100% cltv. Exceptions on a case by case basis but you must present a strong case. The subordination requests are initiated online.
Beneficial (HSBC): 100cltv max. They will review the GFE and request you to lower fees if they deem them excessive.
Saxon: No max CLTV as long as there is a good benefit to the borrower.
I'll post more as I remember them.